The teachers union has been handing out thousands of Barack Obama campaign buttons to its members, sparking a clampdown by education brass.

The Department of Education - which has a long-standing policy barring teachers from wearing campaign buttons in schools - is set to send out an e-mail this week from Schools Chancellor Joel Klein laying down the law.

"Schools are not a place for politics and not a place for staff to wear political buttons," said department spokeswoman Ann Forte...

...United Federation of Teachers official LeRoy Barr told his members in a recent e-mail that union chief Randi Weingarten is fighting the DOE decision.

Officials of the union - which has endorsed Obama - said they didn't know of any schools where button-wearing teachers were told to zip it, but they said they were exploring the matter "to ensure members' rights to free speech and expression."

While department officials said the courts are on their side in the matter, many city teachers say their right to wear partisan buttons is a matter of free speech.

Several cited a landmark 1969 Supreme Court ruling involving students who planned to wear black armbands in protest of the Vietnam War. It affirmed that constitutional rights don't get dropped "at the schoolhouse gate." [For STUDENTS you idiots.]

"It's not teaching kids to vote for Obama; rather, it's showing them the democratic process in action," said Patrick Compton, a social-studies teacher at Lafayette HS in Brooklyn, who said he has been wearing an Obama button handed out by the union.

"It is shocking to me, truly, that in this day and age, the school system wants to diminish, rather than increase, participation in our democratic system."