(CBS) — Representatives of the Chicago Teachers Union late Monday reached a tentative labor deal with the Chicago Board of Education, averting a strike Tuesday morning.

Union President Karen Lewis made the announcement just moments before a midnight deadline would have triggered the dreaded walkout.

“It wasn’t easy, as you all know. Clearly, we had some issues, and there’s some things we’re going to still be working on; but what we found is that we ended up with something that’s good for kids, it’s good for clinicians, it’s good for paraprofessionals, for teachers, for the community,” Lewis said.

Lewis said the four-year deal passed muster with negotiators, and now must be ratified by the union’s House of Delegates and then the rank-and-file membership.

“We don’t sell,” Lewis said, when asked if she would lobby members to approve the deal.

The deal is retroactive to June 2015, when the teachers’ last contract with the Chicago Public Schools expired.

“The highlights are that we have a commitment from the Board of Education on K through 2 class sizes. We have a commitment from the board on layoff and recall provisions,” Lewis said.

There are cost-of-living increases in the third and fourth years of the contract, she said. Current CTU members would continue to get a pension pickup, but new hires would not, she said. Since new teachers would not get the pension pickup, they will get salary adjustments as compensation.

The contract also includes an agreement on class sizes for kindergarten through second grade, meaning teachers would get an assistant in every classroom with 32 or more students.

Beginning next school year, school counselors and special education teachers would no longer be required to perform case management duties.

“The teachers’ hard work will be respected in this contract, and appropriately rewarded. Chicago Public Schools’ finances will be stronger, and on firmer ground, because of this agreement,” Mayor Rahm Emanuel said shortly after the tentative agreement was announced overnight.

The mayor said parents would be relieved and reassured that CPS and CTU worked together to avoid another major strike, which would have been the second in the past four years.

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