KIMBERLY HEFLING, AP Education Writer

WASHINGTON (AP) — The nation’s largest teachers’ union wants Education Secretary Arne Duncan to quit.

Delegates of the National Education Association adopted a business item July 4 at its annual convention in Denver that called for his resignation. The vote underscores the long-standing tension between the Obama administration and teachers’ unions.

A tipping point for some members was Duncan’s statement last month in support of a California judge’s ruling that struck down tenure and other job protections for the state’s public school teachers. Even before that, teachers’ unions have clashed with the administration over other issues ranging from its support of charter schools to its push to use student test scores as part of evaluating teachers.

Duncan wouldn’t comment Monday to reporters while at a White House event.