Los Angeles students and teachers return to class for the new academic year on Thursday under a cloud of apprehension after a summer filled with immigration raids and amid worries that schools could become targets in the Trump administration’s aggressive crackdown.

At 93rd Street Elementary School, teachers, staff and other volunteers patrolled the neighborhood early before school started to see if there were any signs of federal immigration enforcement or agents in the area.

Later, they stepped outside wearing bright orange vests, welcoming students as they arrived and reassuring parents that their children would be safe.

“We wanted to ensure that our families saw that it was safe for them to walk to school and walk back home, and for them to be able to do their drop-off for the first day of school safely,” said Ingrid Villeda, a community coordinator.

Los Angeles Unified School District Superintendent Alberto Carvalho has urged immigration authorities not to conduct enforcement activity within a two-block radius of schools, starting an hour before the school day begins and until one hour after classes let out.

The sprawling district, which covers more than two dozen cities, is the nation’s second largest, with more than 500,000 students. Some 30,000 students are immigrants, and an estimated quarter of them are without legal status, according to the teachers’ union.