The teachers union has buried Mayor Bloomberg under a $2.7 million ad blizzard in the last month, relentlessly attacking his plan to lay off thousands of teachers and repeal the “last in, first out” law.

Now the state branch of the AFL-CIO is piling on, releasing yesterday a $251,000, 60-second radio ad that likens LIFO foes to “extremists like the governor of Wisconsin.”

The United Federation of Teachers’ ad spending mostly covered Feb. 12 to March 17.