Under Impact, the teacher evaluation tool introduced by Michelle Rhee, teachers who receive poor ratings for two straight years get the axe.

Except, you know, they might not.

Nathan Saunders, president of the Washington Teachers' Union, told his membership in a robocall that exceptions will be made for new and veteran teachers alike.

Saunders said that after he learned of slack for new teachers, he "challenged" D.C. Public Schools officials in defense of teachers with lengthier resumes.

"DCPS, effective immediately, will now allow Impact exceptions for all teachers irrespective of years of experience," Saunders said, according to a transcript posted on the WTU website. "Therefore, any minimally effective rated teacher can be granted an Impact exception."

Saunders was out of town on Thursday and unavailable to elaborate on what this means, or how many teachers will be affected. About 500 teachers received minimally effective ratings in the 2009-2010 school year, meaning about 500 teachers are anxiously awaiting the results of this year's evaluations.

Last year, 126 teachers were let go because of their Impact scores, which are based on student test scores and five classroom observations. Termination letters are expected to be sent out any day now.

Either way, the message suggests that the union is pulling heavy weight with DCPS and other city officials who oversee the school system, like Mayor Vincent Gray and D.C. Council Chairman Kwame Brown.

It's also likely to raise eyebrows among critics who say new Chancellor Kaya Henderson lacks the punch that Michelle Rhee gave to education reform in the District.

The union has been fighting Impact tooth and nail through virtually every medium — even court. Henderson, as deputy chancellor to Rhee, developed Impact and has referred to it as her baby.

We have reached out to DCPS for comment and will update as soon as possible.