U.S. Secretary of Education Arne Duncan confirmed today that he opposes fixed terms for school board members. “I think you have to serve at the mayor’s pleasure,” Duncan told me on the phone just now. “If you’re going to have mayoral control, you need to have mayoral control.”

The statement inserts President Obama’s top education official even deeper into New York City’s debate on school governance. Duncan first voiced his support for mayoral control in New York City to the New York Post editorial board in March. He argued that giving the mayor full control over urban public schools is the best way to turn them around.

Many education advocates here, including the teachers union, have pushed for fixed terms as a way to eliminate the mayor’s right to remove any school board member at his pleasure. But the issue is facing opposition from Bloomberg and, most recently, from Assembly Speaker Sheldon Silver, whose latest proposal has school board members serving at the pleasure of the mayor.

Mayor Bloomberg fired three of his appointees on the board, known as the Panel for Education Policy, in 2004 after they said they would oppose a policy he supported. Critics of the mayor call the event the Monday Night Massacre.

Bloomberg has vigorously lobbied against the idea of fixed terms for school board members. Most recently, the mayor personally reached out to Citizens Union members to urge them to reconsider a proposal that would have recommended fixed terms. The watchdog group is set to announce a new proposal today that does not include fixed terms, but does force the mayor to give 90 days notice before firing a disagreeable appointee, according to sources familiar with the watchdog group’s position.

Sources told me that the change of position followed an endorsement from Duncan as well as Bloomberg. But curiously, spokesmen for Duncan have so far not been able to locate the letter that I reported he sent to the Citizens Union. I’ll keep searching for it.