Los Angeles teachers are on strike for the first time in 30 years, leaving over 600,000 students in limbo.

32,000 Los Angeles educators walked off the job Monday in the country’s second-biggest school district. Los Angeles Unified School District has hired about 400 substitute teachers and reassigned more than 2,000 administrators in response.

The strike is not focused on teachers’ salaries. Andrea Cohen, who’s taught at John Marshall High School for 24 years, said “It’s about class size reduction. In other words, hire more teachers. We have 45 to 50 students in a class. It’s unacceptable.”