NASHVILLE, Tenn. (AP) — What began as a bipartisan effort to set new standards in American schools has become a political firestorm, particularly among Republicans.

Establishment voices like former Florida Gov. Jeb Bush praise the Common Core guidelines as a way to improve student performance over time. But many archconservatives, including tea party favorites Ted Cruz of Texas and Rand Paul of Kentucky, say the effort amounts to a takeover of local schools.

Forty-five states initially adopted some part of the standards developed by Republicans and Democrats at the National Governors Association. But legislatures in at least a dozen states have debated measures to repeal or delay the standards.

It's become one more divide between establishment Republicans and the more strident members of their party.