Los Angeles is about to try to prove that class size doesn’t matter. The district, on orders from investment banker Austin Beutner, has hired about 400 substitutes to fill in for thousands of teachers who are preparing to strike on January 10. Let’s see: 400 teachers for 600,000 students. Those are very large classes!

As leaders of Los Angeles Unified School District and United Teachers Los Angeles remain locked in an impasse over a new contract, the district has hired hundreds of substitute staffers to replace picketing educators in the event of a potential strike come Jan. 10. But the move has sparked outrage from the union.

The districts’ preliminary move, alongside the union’s strike preparations, is a sign of the increasing likelihood of a strike that would be LAUSD’s first since 1989 and stands to impact the daily operations of hundreds of schools in the country’s second largest district.

LA Unified Superintendent Austin Beutner said Thursday that the district remains “at the bargaining table” but is actively preparing for teachers’ absence by hiring approximately 400 substitute teachers and fallback instruction for students.

“We have hired substitutes, we have made plans as to alternate curriculums for days that there is a strike but our goal is to make sure schools are safe and open so kids continue to learn,” Beutner said on Thursday. “My concern first and foremost is the safety and well being of our students.”

The move to hire replacement staff drew a sharp rebuke from the union over the last two days.

“It is outrageously irresponsible for Supt. Austin Beutner to force this strike when the district holds $1.9 billion in reserves and it is even more irresponsible to think that 400 substitutes can educate more than 600,000 students,” UTLA said in a statement Friday. “We believe that it is illegal for the district to hire people outside our bargaining unit to teach in LAUSD classrooms.”