PHILADELPHIA (CBS) — The Philadelphia School District has settled an arbitration case and has agreed not to exempt “Promise Academy” teachers from layoffs.

It’s a win for the teachers’ union, who said all along that their contract called for layoffs by seniority and that no group of teachers should be bypassed (see previous stories).

READ MORE: Girl Attacked By Man On Way To School In Atlantic County, Police Say

An arbitrator was expected to rule any day on whether the school district could protect 174 teachers at superintendent Arlene Ackerman’s signature “Promise Academies” from being laid off.

(“Promise Academies” are some of the worst-performing schools in the district that have been singled out for additional resources to turn them around.)

Now, three weeks before school is to begin, the district has settled the case — agreeing to do layoffs strictly by seniority.

READ MORE: Samir Jefferson's Mother Speaks Out After 14-Year-Old Shot 18 Times, Killed In Feltonville

Philadelphia Federation of Teachers’ president Jerry Jordan said Ackerman’s decision created weeks of uncertainty.

“This decision that led to this arbitration was a decision that she made.  And as a result of her decision to violate the contract, we ended up in arbitration and the entire summer left teachers in limbo,” he told KYW Newsradio today.

District spokeswoman Jamilah Fraser said in a statement that the district and union have agreed to withdraw the issue from arbitration, and that teachers assigned to Promise Academies would be reassigned based on their seniority.

Jordan says he hopes many of those teachers who may be laid off as a result can be restored as the district finds money to hire them back.

MORE NEWS: Family, Friends Hold Candlelight Vigil For Slain Temple University Student Samuel Collington

Reported by Mike DeNardo, KYW Newsradio 1060