A state labor board has sided mostly with the Chicago Teachers Union on the issue of Chicago’s longer school day.

Thursday’s decision from the Illinois Educational Relations Board says Chicago Public Schools should cease and desist from offering inducements to teachers to vote for a longer school day. And it should stop dealing directly with teachers over the length of the day and over pay.

The labor board’s decision doesn’t force any immediate changes. But it is significant because it means the union’s unfair labor practice charge now moves to the Cook County Circuit Court. A judge will decide whether to grant an injunction that would force CPS to stop its school-by-school campaign to add 90 minutes to the school day.

It looks like the 13 Chicago schools where teachers have already voted for a longer day will not have to give that up. That only became apparent late in the day Thursday, when the labor board issued its written decision. The teachers union had asked that the school day be dialed back at the 13 schools, and that teachers there be compensated for extra time they’ve already worked. A December labor board hearing will determine whether lengthening the day at those schools was legal.

Schools chief Jean-Claude Brizard said the district will “vigorously” defend the longer school day in court.

“I can tell you, I have 400,000 more kids who are in need of it and I want to keep pushing for it,” Brizard said.

Both CPS and the union say they’re trying to collaborate on the longer day, and each blames the other for failing to do that.