(CHICAGO) Students and teachers in Chicago are heading back to the classroom after the Chicago Teachers Union and the nation’s third-largest school district averted a strike with a late-night tentative contract agreement.

The union had been prepared to hit the picket lines Tuesday morning for what would have been the second major Chicago Public Schools strike since 2012.

But just before a midnight deadline, the union and CPS said Monday it had reached a deal. It still must be approved by the union’s House of Delegates and its full membership, a process that could take weeks.

Mayor Rahm Emanuel and union President Karen Lewis both said they were relieved that the district’s nearly 400,000 students will be in class Tuesday.

The four-year proposal includes cost-of-living increases in the third and fourth year.

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