The Chicago teachers union went on strike Monday morning for the first time in 25 years, CNN reported.

Giving around 350,000 students the day off in the nation's third-largest school district, teachers formed picket lines after 11 months of failed negotiations. The Chicago Public Schools and the 30,000-strong union could not agree on wages, health benefits and job security, The New York Times reported.

With hundreds of thousands of families struggling to find somewhere to send their children, the school district has opened some schools to provide a daycare-like place where around 150,000 students can go. They are providing meals, which is crucial in a district where 84 percent of students qualify for free and reduced price meals.

Karen Lewis, president of the Chicago Teachers Union, said striking was not what they wanted to have to do. “This is a difficult decision and one we hoped we could have avoided,” she said.

Chicago Mayor Rahm Emanuel said he thought the strike was unfair to the students. "The kids in Chicago belong in the classroom," he said.