Mayor Bloomberg is blaming attack ads sponsored by the teachers union for driving down his poll numbers on education.

A poll released yesterday by Quinnipiac University gave Bloomberg some of the lowest grades of his tenure in overseeing the school system, even as voters overwhelmingly supported his latest proposals for attracting top teacher talent.

Only 24 percent of those surveyed called the mayor’s takeover of the schools a success, while 57 percent called it a failure.

By 61 percent to 26 percent, voters said they disapproved of the mayor’s “handling” of the schools system.