Teachers in Chicago are on strike for the first time in 25 years on Monday after school district and teachers union leaders failed to come to an agreement on a contract over the weekend.

More than 26,000 teachers and support staff were expected to hit the picket lines at 6:30 a.m. Monday.

The walkout in the nation's third-largest school district posed a tricky test for Mayor Rahm Emanuel and his city, as parents and school officials begin the task of trying to ensure nearly 400,000 students are kept safe.

This is not a strike I wanted. It was a strike of choice ... it's unnecessary, it's avoidable and it's wrong.

- Rahm Emanuel, Mayor of Chicago

School officials said they will open more than 140 schools between 8:30 a.m. and 12:30 p.m. so children can eat lunch and breakfast in a district where many students receive free meals. The district asked community organizations to provide additional programs for students, and a number of churches, libraries and other groups plan to offer day camps and other activities. But it's not clear how many families will send their children to the added programs.

Many Latino immigrant parents in Chicago's Pilsen neighborhood are especially worried.

Near Manuel Perez Jr. Elementary School in Pilsen, an enclave of Mexican immigrants where the public school plays a central role for almost everyone, the concerns were of a long-term nature. Working-class parents say they now need to find a family member or someone to watch their children while they work, but their bigger fear is children will lose ground on attaining the better life the parents uprooted and crossed borders to pursue.

Police Chief Garry McCarthy said he was deploying police officers to those sites to ensure kids' safety but also to "deal with any protests that teachers may, in fact, have" while protecting their rights. He also was taking officers off desk duties and redeploying them to the streets to deal with potential protests — and thousands of students who could be on the streets.

Emanuel said he will work to end the strike quickly.

"We will make sure our kids are safe, we will see our way through these issues and our kids will be back in the classroom where they belong," Emanuel said Sunday night, not long after the union announced it was going on strike. "I would like all the parties to do right by our children. ... Our kids belong in the classroom. The negotiators belong at the negotiating table and finish their job."

The two sides were not far apart on compensation but were on other issues, including health benefits — teachers want to keep what they have now — and a new teacher evaluation system based partly on students' standardized test scores, Chicago Teachers Union President Karen Lewis said.

"This is a difficult decision and one we hoped we could have avoided," she said. "We must do things differently in this city if we are to provide our students with the education they so rightfully deserve."

"This is not a strike I wanted," Emanuel said. "It was a strike of choice ... it's unnecessary, it's avoidable and it's wrong. "

Both Emanuel and union officials have much at stake. The walkout comes at a time when unions and collective bargaining by public employees have come under criticism in many parts of the country, and all sides are closely monitoring who might emerge with the upper hand in the Chicago dispute.

The timing also may be inopportune for Emanuel, a former White House chief of staff whose city administration is wrestling with a spike in murders and shootings in some city neighborhoods and who just agreed to take a larger role in fundraising for President Barack Obama's re-election campaign.

As the strike deadline approached, parents spent Sunday worrying about how much their children's education might suffer and where their kids will go while they're at work.

"They're going to lose learning time," said Beatriz Fierro, whose daughter is in the fifth grade on the city's Southwest Side. "And if the whole afternoon they're going to be free, it's bad. Of course you're worried."

School board President David Vitale first announced Sunday night that talks had broken off, despite the school board offering what he called a fair and responsible contract that would cover four years and meet most of the union's demands. He said the talks with the union had been "extraordinarily difficult."

Emanuel said the district had offered the teachers a 16 percent pay raise over four years, doubling an earlier offer.

Lewis said she would not prioritize the issues, saying that they all were important to teachers.

That included concern over a new evaluation that she said would be based too heavily on students' standardized test scores, which she said would be unfair to teachers because it could not adequately account for outside factors that affect student performance, including poverty, violence and homelessness.

She said the evaluations could result in 6,000 teachers losing their jobs within two years.

City officials said they did not believe that was true but said the union would not tell them how they came to that conclusion. Emanuel said the evaluation would not count in the first year, as teachers and administrators worked out any kinks. Schools CEO Jean-Claude Brizard said the evaluation was mandated by state law but "was not developed to be a hammer," but to help teachers get better.

The strike is the latest flashpoint in a very public and often contentious battle between the mayor and the union.

When he took office last year, Emanuel inherited a school district facing a $700 million budget shortfall. Not long after, his administration rescinded 4 percent raises for teachers. He then asked the union to reopen its contract and accept 2 percent pay raises in exchange for lengthening the school day for students by 90 minutes. The union refused.

Emanuel, who promised a longer school day during his campaign, then attempted to go around the union by asking teachers at individual schools to waive the contract and add 90 minutes to the day. He halted the effort after being challenged by the union before the Illinois Educational Labor Relations Board.

The district and union agreed in July on how to implement the longer school day, striking a deal to hire back 477 teachers who had been laid off rather than pay regular teachers more to work longer hours. That raised hopes the contract dispute would be settled soon, but bargaining continued on the other issues.

Based on reporting by the Associated Press.

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