The strikes were announced shortly after President Donald Trump told reporters in the Oval Office that "you're going to find out" if the U.S. will respond.
Los Angeles Unified School District administrators and United Teachers Los Angeles ratified their respective new labor contracts with the district, their unions announced.
Educators in the Little Lake City School District officially walked out after months of what union officials called stalled contract negotiations.
A strike has been averted after LAUSD reached a tentative agreement with three unions, meaning schools were open Tuesday.
LAUSD is continuing last-minute contract negotiations on Monday to avert a looming strike and keep campuses open for hundreds of thousands of students.
While tentative agreements represent a win for teachers and administrators, there is still one union awaiting its own agreement -- which means there could still be a strike with tens of thousands of other school workers.