The San Francisco Unified School District closed all 120 of its schools Monday and offered independent study to some of the district’s 50,000 students.

About 6,000 public schoolteachers in San Francisco went on strike Monday, the city’s first such walkout in nearly 50 years.

The strike comes after teachers and the district failed to reach an agreement over higher wages, health benefits, and more resources for students with special needs. The San Francisco Unified School District closed all 120 of its schools and said it would offer independent study to some of its 50,000 students.

“We will continue to stand together until we win the schools our students deserve and the contracts our members deserve,” Cassondra Curiel, president of the United Educators of San Francisco, said at a Monday morning news conference.