Class is canceled in Chicago Thursday, as tens of thousands of teachers decided not to show up to school.

25,000 Chicago educators will not be teaching Thursday, instead they'll be fighting for smaller class sizes and better pay and benefits.

Jesse McAdoo, a teacher, said "I have 30 students in my classroom. Half first grade, half second grade."

The Chicago Teacher's Union called the strike after months of negotiating with the nation's third-largest school district failed.

The city's mayor says the union's demands would cost the city $2.5 billion, which it can't afford.

Canceling class Thursday will affect nearly 400,000 students. Team practices, field trips, tutoring, and other after school activities will also be canceled.

The district says it still plans on keeping schools open Thursday and staffed with non-union employees for students who need a safe place to spend the day.