This doesn't mean 20,000 teachers will actually get laid off - just that they could be. Districts often issue extra pink slips just to play it safe, because after this deadline, they lose staffing flexibility. Then, districts tell some teachers they can keep their jobs after all, once the districts have a better idea of what their budgets will look like.
But this year could be different. The CTA's Eric Heins says everything depends on Governor Jerry Brown's November tax initiative:
Heins: "If it doesn't pass, it means an additional $5 billion in cuts to schools in California. Kinda hard to figure out where that's gonna happen, because they've been cut so much already, there's not much left."
The 20,000 layoffs don't include district employees other than teachers, like janitors and support staff.
Sacramento City Unified and San Juan Unified are both among the top 10 school districts issuing layoff notices, with several hundred each.