The state plans to cut school funding by more than $350 million. The teachers union expected about 30,000 teachers to participate.
Administrators said classes will go on, but they could be delayed, and students will have to be supervised by aides and other administration.
"We support the message that teachers are trying to send. We just don't support the action. We want them in the classrooms, working with our children. They're going to take away from their instructional time, which is critically need in here L.A., and nothing is more important than the safety of our children," said LAUSD supervisor David Brewer.
The union president said the teachers will not be paid for picketing.
School officials urged teachers not to take part in the walkout, and lawyers went to court and filed for a temporary restraining order.
Community group called on parents and the public to support the UTLA walkout.