Shortly after 10 a.m. on day 2 of the Great School Strike of 2012, the long stretch of Western Avenue in front of Lane Tech was blanketed in red. More than 100 striking teachers at the elite North Side high school, all wearing the official color of the Chicago Teachers Union, paraded up and down the street, clanging cowbells and chanting, “Hey, hey, ho, ho! Rahm Emanuel’s got to go!” Cars and every CTA bus, police car, and garbage truck that passed honked in support.

Stranding some 350,000 students, the September walkout was the first teachers’ strike in the Chicago Public Schools, the country’s third-largest school district, since 1987. It cast a national spotlight on the influential reform movement that is bent on reshaping American public schools—and the dogged efforts of the Chicago Teachers Union and its little-known first-term president, Karen Lewis, to resist it.

After seven school days off, Chicago’s kids returned to their classrooms even though the contract was still being negotiated. In the tentative agreement, the union successfully blocked some of Mayor Emanuel’s most aggressive attempts to reform CPS by fiat. (More on that later.) What is not controversial is that CPS desperately needs improvement. In 2011, nearly 40 percent of Chicago’s public high-school students failed to graduate within five years, students’ ACT scores averaged an abysmal 17.2, and the school day and year were among the shortest in the nation. (Under recent state law, time in class is now on par with that in other big cities; see chart, below right). Meanwhile, some observers found the union’s fight for raises unseemly at a time when the city faces huge deficits.

The strike was the highest-profile pushback to date against the reform movement, which has attacked bad teachers and the unions that protect them. Lewis, a 59-year-old chemistry teacher and one-time standup comedian with a penchant for impolitic remarks, emerged as the flag bearer of the resistance, inspiring some Chicagoans and enraging others. “This fight is not about Karen Lewis,” she intoned at a Labor Day rally days before her more than 29,000 members took to the picket lines. “Let’s be clear: This fight is for the very soul of public education, not only in Chicago but everywhere.”

The Chicago Teachers Union headquarters occupy a suite of generic offices on the fourth floor of the Merchandise Mart, the art deco citadel on the north bank of the Chicago River. Lewis was in good spirits when I met her there in June, at the beginning of a tense summer of negotiations. Her dreadlocked hair was pulled back in a ponytail, and her nails were painted green with silver sparkles (she changes the color often). The room was littered with souvenirs: A glass block etched with the words “Bitch Brick” rested on her desk, and a pair of blue boxing gloves hung on the wall, a gift from a friend after Lewis told the Chicago Tribune she was going to buy some following the announcement of the mayor’s education team.

A Halloween mask of Rahm Emanuel’s face was tacked onto a shelf in front of Lewis’s desk, staring straight at her and leaving little doubt that she considers the mayor her chief opponent. Yet Lewis marveled that she and Emanuel don’t like each other more. “I don’t understand it,” she said, shaking her head. “We should be best friends. We have way more in common than we don’t.”

Shortly before he took office in May 2011, Emanuel invited Lewis to a dance performance and dinner at Henri, the upscale French restaurant across from Millennium Park. She said they had the same tastes—they both drank malbec and ordered the lamb—and talked about their shared love of ballet. They are also both Jewish. Raised Lutheran, Lewis converted in the early 1990s when she was “looking for something spiritual” and says she was drawn by the “idea that you could question God.”

The evening was meant to establish a working relationship. But the conversation took a turn when, according to Lewis, Emanuel said that 25 percent of students in CPS—or nearly 100,000 kids at the district’s current enrollment—were “never going to make it and that he wasn’t going to throw money at the problem.” The comment came to light a year later when Lewis talked about it in an on-camera interview with local NBC reporter Mary Ann Ahern; Emanuel denied it, calling the story “totally false.” The episode likely damaged whatever trust they had established.

“I don’t think he really cares about poor people, people of color,” Lewis says today of the mayor, reflecting on the incident. “I think he feels he needs to have a decent education plan so that people will want to live in Chicago.”

That she is willing to publicly and rather starkly characterize the battle with the mayor over education reform as a kind of class war hints at the ideological chasm between the two leaders. (Despite numerous requests, the mayor’s office and CPS CEO Jean-Claude Brizard declined to comment for this story.)

Almost soft-spoken in person, Lewis is a natural performer and a forceful orator, often building up a head of steam around a single point. She also has a tendency to take things too far. The unfiltered Lewis was on full display in a speech she gave to a convention of teachers last fall in Seattle, where she committed the gaffe that introduced her to the greater public. “I am the only black woman in the class of 1974 from Dartmouth College,” she said, only to deflate her own accomplishment in the next breath with a sarcastic “woo” and a glance. “People are impressed,” she continued. “Let me tell you, I spent those years smoking lots of weed. Self-medicating.” The crowd tittered.

This was just three minutes into a 32-minute ramble that veered from the bankruptcy of Milton Friedman–style capitalism to billionaire education reformer Penny Pritzker to the now-infamous mocking of the speech impediment of Arne Duncan, the U.S. secretary of education. “This guy who has the nerve to stand up and say, ‘Education is the thivil rights ithue of our time,’ ” Lewis said, imitating Duncan. “You know he went to private school because if he had gone to public school he’d have had that lisp fixed.”

Lewis didn’t want to talk about the speech when I brought it up. But when pressed, she said the controversy marked the first time she realized she was a public figure whose personal actions could undermine her professional cause. “That was a turning point for me to understand that I wasn’t just Karen Lewis, schoolteacher, any longer,” she told me. “That this was serious and that there are people who are trying to destroy public education and would use me to do that for them.”

The older of two daughters of Chicago public school teachers, Karen Lewis (née Jennings) grew up in modest comfort in Hyde Park at the height of the civil rights era. Her mother was the daughter of a surgeon who served as the chief of staff at a hospital for blacks in St. Louis. Her father, the son of a bus driver, came from segregated Tulsa, Oklahoma. She was steeped in social justice thinking from an early age. “My parents never placed limitations on me,” Lewis says. “As far as they were concerned, I could be the president of the United States.”

Or a professional baseball player. When Lewis was born, her father bought her three mitts—one for each hand and a catcher’s glove—and taught her to bat left-handed to give her an advantage in hitting to the major league’s shorter right fields. “I grew up thinking I could play major-league baseball, not knowing that because I was a girl that would not be an option,” Lewis says. “He never, ever thought that I should think about those things.” The news of the day dominated dinnertime conversation: “It didn’t matter how old you were, if you wanted to talk at the table you had to be on top of it.”

Chicago was roiled by social unrest while Lewis attended high school. Protests against the Vietnam War were raging, and the city—the South Side in particular—was reeling from the 1969 killing of Fred Hampton, a Black Panther, by police. Two years earlier, Lewis had entered the newly opened Kenwood High School, a freshman in its second class of students (along with Chaka Khan and Mandy Patinkin, a year ahead). She soon began participating in black-student walkouts, which were happening at other city schools.

“We were upset that the curriculum lacked blacks in any kind of position of power,” she says. “There was no African American history. And we wanted better food in the cafeteria.” Her father would often chauffeur Lewis and her friends to evening organizing meetings. “My parents understood how important it was for us to be involved,” she says. “Just don’t get arrested! That’s all they cared about.”

Lewis left Kenwood after her junior year, without graduating, to attend Mount Holyoke College, the prestigious all-women’s school in Massachusetts, which had offered her early admission and a scholarship. A wave of student protests had swept across college campuses during the 1969–70 school year, and a riled-up Lewis arrived at Holyoke the following fall ready to join them—only to find she was a year too late.

Lured by a boyfriend, she transferred to Dartmouth in 1972, the first year the school admitted women, and hated it. “What a lot of people don’t realize is when Dartmouth went coed, the students [were] against it. The only people that voted for it were the trustees,” she says. “So it was just a hostile environment.”

During the fall of her senior year, on a trip to visit her grandparents in Oklahoma, she met Arnold Glenn, a friend of the family. A real-estate inspector six years her senior, “he was gorgeous, and he was grown,” Lewis says. She married Glenn immediately after graduating.

Living in Tulsa was an alienating experience. “It felt like the black revolution had never hit,” she says. It was there that she was called a nigger for the first time in her life, by a young child on the street. “I just went nuts,” she recalls. “I completely went off on this kid.” The child’s parents, she says, looked at her as if they didn’t understand why she was upset.

Lewis fumbled around in odd jobs—a social worker in a methadone clinic, a computer programmer, a substitute music teacher—until 1980. By then separated from her husband, she left Oklahoma to live in Barbados for a year and fell in love with the island’s communal culture. “I was poor, really poor, and it was OK because in Barbados nobody will let you starve,” Lewis recalls. “I cannot tell you the warmth of this environment.”

She returned to Tulsa but soon moved back to Chicago; Lewis and Glenn divorced in 1984. She enrolled in medical school at the University of Illinois at Chicago, intent on returning to Barbados as a doctor, one of the few jobs outsiders could hold in the country. She flunked out after two years. “Med school is something you have to have a calling for. You have to really want to be a doctor. I just wanted to live in Barbados!” she says, cackling.

Older than her classmates by ten years, Lewis enjoyed the courses but chafed at the hours of studying and the testing regimen. “I would read these multiple-choice questions and they were crazy to me. It was like Greek,” she says. “I was like, ‘Why can’t you just ask me?’ At Dartmouth, we didn’t have any multiple-choice tests. You just wrote. You defended an argument.”

Medical school may have been a bust, but through it Lewis discovered that she loved chemistry. “The beauty of chemistry to me—which is different from, say, biology—is that if you forget a step, you can think your way through it,” she says. “It teaches you to think logically. If [an experiment] doesn’t work, you get to reflect and say, ‘Where in my thinking, where in my process, did I make a mistake?’ ”

Lewis is quick to make the connection to the current battle over education reform, which in her view is not a rational discussion about how to fix schools but rather a political fight for control. “People have this ideology about education that’s not based in research, in a real understanding of how things work,” she says. “I have no patience for that, because it’s just silly. Where’s the evidence?”

To make ends meet, Lewis worked at a video store in Hyde Park and briefly flirted with standup comedy, scoring the occasional gig at the Woodlawn Tap. In 1987, she landed a job at Sullivan High School in Rogers Park as a substitute chemistry teacher and was hired full-time the following year. (She had previously resisted teaching, she says, so as not to follow directly in her parents’ footsteps.) Around that time, Secretary of Education William Bennett famously derided Chicago’s school system as the “worst in the nation,” citing the 43 percent high-school dropout rate and dismal ACT scores.

But Lewis says Bennett’s view wasn’t her experience. A neighborhood school on the North Side, Sullivan was using the Paideia program, a holistic curriculum that included discussion-based seminars and analysis of primary sources. “Instead of using the textbook to look at Boyle’s law [at constant temperature, the pressure and the volume of a gas are inversely proportional], we could read what Boyle wrote,” Lewis explains. “It promoted critical thinking like you wouldn’t believe.” Assigned a seventh-grade biology class, she taught using her anatomy and physiology textbooks from med school.

Three years later, Lewis moved to Lane Tech, the city’s prestigious selective enrollment math and science academy. She found that Sullivan and Lane were a case study on the difference curriculum can make: Lane was using the kind of drill-based, rote exercises that she had found so dispiriting as a medical student. “What I found at Lane was that kids were really good at memorizing and taking multiple-choice tests,” she says. “They were not as good at critical thinking, like the kids at Sullivan.” (Lewis, who is childless, says that she wanted to be a parent but the timing never worked out.)

Lewis thrived at Lane, however, where she was one of nine chemistry teachers in the robust science department. In 1995, she started dating John Lewis, a physical education teacher at Lane (initially set up as prom dates by students, they married in 2001). She also became an active member of the teachers’ union, in part because she objected to what she calls the principal’s “bullying” management style.

That same year, the Illinois General Assembly gave control of the Chicago school system to Mayor Richard M. Daley to speed reform. He appointed Paul Vallas, his budget director, to be the new CEO of CPS. Vallas slashed costs, ended social promotion, and began a serious data-gathering campaign to track student progress.

Arne Duncan succeeded Vallas in 2001 and, three years later, launched Renaissance 2010, the most ambitious school reform effort in Chicago’s modern era. The signature education initiative of Daley’s 22-year mayoralty, the plan sought to create 100 high-quality schools by opening new ones and closing those that were underenrolled or considered beyond redemption. Renaissance 2010 added subject-specific magnet schools and a raft of new charter schools—publicly funded institutions run by outside companies that usually admit students by lottery.

Though many rank-and-file teachers opposed the plan, the mayor assuaged union leadership with lucrative contracts. “Mayor Daley simply paid for cooperation,” says Robert Bruno, a professor of labor studies at the University of Illinois at Chicago. “There were good bread-and-butter contracts, but teachers had to relinquish control of the classroom.”

By the time Lewis left Lane in 2006 to teach at King College Prep, near her home in the South Side neighborhood of Oakland, she was inching toward retirement. Eager to retreat to her time-share in Hawaii with her husband, who had retired in 2003, Lewis curtailed her union involvement. But in 2008 she attended a book group with a handful of teachers, many of whom worked at schools that had been targeted for closure under Renaissance 2010. They discussed The Shock Doctrine, Naomi Klein’s 2007 polemic about the spread of the privatization movement. Lewis found new purpose in organizing teachers against Daley’s sweeping reform measures.

The reading group evolved into a faction of the Chicago Teachers Union called the Caucus of Rank-and-File Educators (CORE). They believed that a member-driven union could counter the encroachment of reform-minded philanthropists and give teachers a voice in shaping the direction of schools. “We increasingly had this sense that if we didn’t do something, you could wind the film forward ten years and there wasn’t going to be much left of our public school system or our union,” says CTU’s vice president Jesse Sharkey, who convened the reading group.

In 2010, CORE put Lewis forward as a candidate to run against the two-term incumbent union president, Marilyn Stewart. “We’re in an existential fight here and who better to do that?” Lewis says. “I feel like this was a responsibility—when called, you have to come.”

She won by a landslide, in large part due to her ability to tap into how teachers feel. “I don’t think anyone was under the impression that Karen was going to be the operations person,” Sharkey says. “She provokes both a sense of pride and a stiffening up of the spine and a willingness on the part of our members to take a stand.”

Lewis’s term began in June 2010. Terry Mazany, president of the Chicago Community Trust, became the interim CEO of CPS shortly after. “She is at the intersection of ideological, social, and political divides in our community,” Mazany says of Lewis. “But underneath it all there beats a human heart who has a real commitment and passion for young people and their ability to gain an equitable education. The only tool she has is the union.”

Within weeks of declaring his candidacy for mayor in November 2010, Rahm Emanuel announced an ambitious agenda to improve Chicago’s schools. The platform included a number of free-market-influenced initiatives, such as merit pay, and a longer school day. “Rahm, being Rahm, wanted to make Chicago the epicenter for reform nationally,” says Tim Knowles, the director of the University of Chicago Urban Education Institute and a charter school operator who has advised Emanuel on education. “No other big city carries that mantle now.”

The mayor did not try to hide his cards. His campaign was cochaired by Juan Rangel, the head of the growing UNO charter school network, and supported by some of the city’s wealthiest education reform advocates, including venture capitalist Bruce Rauner and Penny Pritzker, whom Emanuel later named to the Chicago Board of Education. Shortly after he was elected, Emanuel announced that Jean-Claude Brizard would be the new CEO of CPS. A former New York City science teacher, Brizard had clashed with the teachers’ union as superintendent of schools in Rochester, New York. He is a graduate of the Broad Superintendents Academy, a training program for promising public school leaders, founded by the billionaire reformer Eli Broad.

In his inaugural address on May 16, 2011, Emanuel promised swift action: “As some have noted, including [my wife], I am not a patient man. When it comes to improving our schools, I will not be a patient mayor.” A month later, Emanuel’s appointed school board said the district could not afford the 4 percent raises teachers were scheduled to receive and voted unanimously to rescind them.

Lewis was dismayed but not surprised. “From the very beginning he was pretty clear about what his agenda was,” she says of Emanuel. “His agenda is the same agenda that we have seen throughout the country, which is an agenda of blaming teachers for everything that’s wrong with public education systems, not looking at any of the systemic issues.”

Before taking office, Emanuel helped shepherd a bill through Springfield that gave him carte blanche to implement his education plan. Signed into law in June 2011, Senate Bill 7—or SB7, as it is often called—was a direct shot at many of the benefits teachers had accumulated through decades of collective bargaining: It stripped senior teachers of protections against firing and linked tenure to performance reviews. SB7 also raised the strike threshold considerably, requiring the approval of 75 percent of all union members, and gave Emanuel the power to unilaterally lengthen Chicago’s school day and year. (Before the bill, Chicago schools averaged five hours and 45 minutes from bell to bell, according to CPS. Elementary schools now have seven hours a day; high schools, seven and a half. The new school year lasts 180 days, up from 170.)

Lewis was involved in drafting SB7, but she has since disavowed it. When I asked about her initial support for the bill, she interjected, “No, no, no, no, no! I am sick of hearing this support-the-bill crap. We didn’t have a choice, OK?” The legislation, according to Lewis, “was a steamroll job,” orchestrated by Jonah Edelman, the CEO of Stand for Children, a business-backed national reform group based in Portland, Oregon. “His little tiny self was down in Springfield pushing this, pushing that, buying up all the lobbyists. . . .We were told there would be a bill, and how hard it would be or how easy it would be depended on what we did.”

Indeed, at a panel discussion at the 2011 Aspen Ideas Festival, a few weeks after Governor Quinn signed the bill, Edelman explained how Stand for Children used its deep pockets to hire 11 lobbyists—“including four of the absolute best insiders and seven of the best minority lobbyists”—and curry favor with legislators. The goal, he said, was to show teachers’ unions “that we had clear political capability to potentially jam this proposal down their throats.” Captured in a video that went viral, he described Lewis as a “die-hard militant” and said she had made a “tactical mistake” in agreeing to the heightened strike vote requirement. “The unions cannot strike in Chicago,” Edelman boasted. “They will never be able to muster the 75 percent threshold to strike.”

The CTU proved Edelman wrong in May of this year when 90 percent of its members voted to authorize a strike. Behind the scenes, the SB7 experience may also have poisoned the well for the contract negotiation. Certainly, Lewis says, it hardened her against collaborating with education reformers going forward. “The unions have agreed to things that are absolutely terrible for their members because they’ve tried to work with these folks,” she says. “But it is never enough. These people want complete and total control. They want to actually destroy public education.”

With the longer school day now required by law, Lewis wanted to discuss with the mayor what the new day should include before the change went into effect in the fall of 2012. She had said that the union didn’t object to a longer day as long as it could be a “better day” that brought to schools neglected noncore subjects such as arts, physical education, and world languages. “The idea of taking the elementary school day and just elongating it made no sense to me,” Lewis says.

Seeking clarity, she met with Emanuel at his office in August 2011. It didn’t go well. “I asked him about it, and his basic response was, ‘Well, I can’t have kids on the street at 2:30.’ And I’m like, ‘So this isn’t about education. This is a baby-sitting issue, a warehousing issue,’ ” she recalls. “And then he got angry at me and cussed me out.” Three weeks later, Lewis reported the exchange to the news media.

For Lewis, the final straw came right on the heels of that meeting. At the end of the summer, the mayor announced his Longer School Day Pioneers Program, which offered $150,000 and a nearly 2 percent teacher raise to elementary schools that elected to waive the hours in their union contracts and add 90 minutes to their day—a full year before the law was scheduled to take effect. Lewis refers to this episode as the mayor “bribing” her members.

As the strike dragged on in September, a resolution hinged on a tricky question: How do you measure a teacher’s quality?

Teachers play an important role in determining students’ success, which is why current reformers focus on weeding out the bad ones and keeping the good. They believe that student performance on standardized tests is a fair metric by which to judge a teacher’s effectiveness in the classroom. Hence the push to link test scores to teacher evaluations. Merit pay—teachers are rewarded for improving scores in lieu of automatic annual raises—is the carrot. The stick is that teachers who fail to deliver may be fired, and schools that stagnate can be closed.

This data-driven approach is rolling through a growing number of school districts across the country, including those in Washington, D.C., Denver, and Los Angeles. A bipartisan cause (witness the huzzahs Emanuel received from Mitt Romney and Paul Ryan during the strike), it is also backed by some of the country’s wealthiest philanthropists.

However, Lewis and the union argue that test scores are a crude tool for gauging teacher quality. So-called value-added scores—a metric used to evaluate teachers based on student gains on standardized tests—adjust for socioeconomic disadvantages. But Lewis says value-added scores don’t go far enough and effectively hold teachers in poor neighborhoods accountable for factors beyond their control, such as homelessness and violence. “If I’m teaching kids who have more need than my value-added scores [account for], their test scores aren’t going to be as high as those of kids at a different level,” Lewis says. “Yet there’s no consideration made for that.”

She has an ally on this front in Mazany, who calls the reliance on metrics the “tyranny of testing.” “Research study after research study shows you can’t crosswalk from testing what a student knows to the inference for teacher quality,” he says. “And that creates further tension between the district and the teachers, because teachers know this research and know that it’s fundamentally unfair to evaluate teachers based on these test data.”

(A recent study that tracked 2.5 million students over 20 years was not as conclusive as some reformers made it out to be: It found that teachers with high value-added scores on standardized tests indeed produced students with better outcomes as adults. However, the study’s authors, economists at Harvard and Columbia, cautioned that other methods of judging teacher quality, such as classroom observation, were not tested and “might be even better predictors of teachers’ long-term impacts than value-added scores.”)

Lewis also objects to the insinuation by some in the reform movement that teachers don’t want to be evaluated at all: “We crave real evaluation so we can get better.”

On the last day of the strike, Lewis told Chicago that she would like to see teachers rated by their peers. But she said that presenting an alternative evaluation model to CPS and the board goes beyond the scope of her role as chief negotiator for the union, especially since she could only argue for the terms under which the new state mandate would be carried out. (In the tentative contract between the city and the union, student test scores will count for up to 30 percent of a teacher’s overall performance rating, down from a maximum of 40 percent in an earlier version.)

But Lewis’s concerns are much broader than teacher evaluations. She is “really scared about what’s happening to public education,” says Jeff Wright, who was the principal at King College Prep when Lewis worked there (he is now a district administrator for the Sauk Prairie Schools in Wisconsin). Specifically, he says, she fears the threat posed by charter schools, which are not required to serve children who don’t speak English or who have behavioral problems. Says Wright, “I think Karen believes she has to speak on behalf of a public education that teaches everyone, regardless of who you are, [and is] accessible to all.”

CPS currently has 119 charter schools, whose faculty are not allowed to join the CTU. The district plans to create 60 more over the next five years, according to a grant application filed with the Bill & Melinda Gates Foundation, and has threatened to close more than 100 failing or undersubscribed traditional public schools in 2013. This despite the fact that Renaissance 2010 did not create the radical improvement hoped for by its supporters. A 2009 analysis by the Chicago Tribune showed that standardized test scores at Renaissance 2010 elementary schools were nearly identical to the overall CPS average, and scores at the high schools were below average.

After the union’s house of delegates finally voted to call off the strike on September 18, Lewis met the crush of media gathered at a West Side union hall for the occasion. With a big smile and weary eyes, she said she felt “great” about the strike, even if the resulting deal didn’t satisfy all of her members, because it made the point that “the people that are actually working in the schools need to be heard.”

Asked by a reporter if she felt pressure had been lifted from her shoulders, Lewis let out a small laugh. “You know I haven’t had a chance to have any pressure taken off me since I started this job,” she said, noting that she expects to clash again soon with CPS over school closures.

She has found some solace, if not much rest, in her faith. Lewis got back in the habit of attending weekly services at her synagogue a few years ago, and she says her religious study has been especially important during the last tumultous year. “I look forward to Saturday morning; I just can’t wait. My Hebrew reading is getting better,” she says. “It has been very helpful during these times of tribulations and trials to be focused on something not yourself.”

Her bat mitzvah is scheduled for next June, and Lewis can’t help but see the portion of the Torah she’s studying—Shelach—through the lens of her fight for teachers. “It’s a perfect portion for me,” she says. “It’s about people being told they can’t do something, and they were able to.”