Teachers unions have a well-deserved reputation for exercising political clout. With a nearly unparalleled ability to raise cash and organize their ranks, they have elected school boards, influenced legislation and helped set the public school agenda in major American cities for decades.

Now, that clout is in question.

A nationwide school reform movement with bipartisan support has collided head-on with unions over three ideas that labor has long resisted: expansion of charter schools, the introduction of merit pay for teachers and the use of student test scores in teacher evaluations.

Mitchell Landsberg, Los Angeles Times