NEW YORK – New York City municipal unions waited to negotiate new contracts until Bill de Blasio was mayor and with good reason: they knew the Progressive Democrat would give them whatever they wanted.

And did he ever, awarding retroactive raises for three previous years to the city’s teachers.

But the mayor didn’t include retroactive raises for teachers who resigned over the past few years, and they are suing to get what they consider their piece of the pie.

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The New York Post reports:

Teachers shut out of retroactive pay raises under the new union contract are looking to claw their way into the windfall with a class-action lawsuit that could cost taxpayers as much as $35 million, The Post has learned.

About 4,000 teachers who worked between 2009 through 2011 — the years covered by the back-pay deal — and left before their eligible retirement are excluded under the nine-year contract approved by the United Federation of Teachers and Mayor de Blasio.

Some 4,200 teachers who called it quits in 2012 and 2013 also might claim the retro pay, which would be 8.16 percent of their final salaries.

That’s likely tens of millions of dollars.

“That’s the raise we should have gotten all along. Now we’re not getting it for whatever reason,” former teacher Theresa Pepe told the paper.

“We’re not asking for money that we didn’t work for. The point is we deserve that money.”

These people quit before they were eligible for retirement. If anybody deserves a retroactive raise (and that’s highly questionable), it’s the teachers who stuck it out during the lean years, lived without raises and took pay cuts.

The people who jumped ship in the middle of the journey deserve no reward at all.