BROOKLYN, N.Y. – The United Federation of Teachers – the union that feeds off of New York City schools – recently issued a report warning that nearly half of the city’s public school teachers leave the district in their first six years, either to work in other districts or to pursue a different profession.

UFT President Michael Mulgrew said that trend spells trouble for the district.

“I don’t believe our school system is going to get better if we continue to lose half the teachers who walk into New York City schools,” Mulgrew said.

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New York City  has made similar statements recently.

Mulgrew, of course, blames teacher attrition on a lack of across-the-board pay raises for New York City educators.

But the , a nonprofit education advocacy group, says Mulgrew’s concern about the number of teachers leaving the district (and profession) is misplaced.

TNTP blogger Ariela Rozman writes that the real problem is the loss of quality teachers, who leave because they are paid the same as less talented or dedicated peers – not the thousands of mediocre or poor teachers who correctly determine that they are in the wrong profession.

“Good schools cannot be run without good teachers, yet we let them slip out the door every day,” Rozman writes. “We lose far too many outstanding early career teachers who could give us years of fantastic service. We lose amazing veteran educators who are pillars of their schools but don’t get the recognition or opportunities for advancement they deserve.”

Rozman correctly points out that as tragic as it is for top teachers to walk away from the classroom, it’s equally tragic “when a teacher who simply is not up to the job stays in place year after year. Turning a blind eye to quality and focusing on overall numbers doesn’t help students.”

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Trying to retain all teachers – regardless of their classroom performance – is a waste of time, according to Rozman.

“Making quality judgments about teacher retention based on one number – the percentage of teachers who stay or leave – doesn’t make much sense,” she writes. “It’s like basing a restaurant review solely on the size of portions, not whether the food is any good.”

She concludes that if UFT leaders and Mayor de Blasio are genuinely concerned about the alleged retention crisis, they’ll focus solely on retaining the quality teachers.

Allowing schools to base teacher pay on what the market demands – instead of what a collectively bargained union contract requires – would probably go a long way toward retaining top educators in the all-important subject areas of math and science.

Merit pay plans could also help accomplish this goal.

The UFT will never agree to such plans because that would be an acknowledgment that educators aren’t the equal, interchangeable workers that labor leaders portray them as.