In a political embarrassment for Republicans, House GOP leaders on Friday abruptly cancelled a vote on a bill to update the George W. Bush-era No Child Left Behind education law after struggling to find support from conservatives.

The bill would keep the annual testing requirements on schools but would give more freedom to states and districts to spend federal dollars and determine how to identify and fix failing schools. But conservative opponents said it doesn't go far enough to allow states and districts to set education policy. Such conservative groups as Heritage Action for America and Club for Growth are among opponents..

"We have a constitutional duty as members of Congress to return education decisions to parents and states," Justin Amash, R-Mich., wrote this week on Facebook.

Democrats also dislike the bill and said it would go too far in reducing the federal government's responsibility to ensure that poor, minority, disabled and non-English speaking students go to good schools and that billions of federal education dollars are spent wisely. The White House threatened to veto the bill, calling it "a significant step backwards."

Senior Republican officials said it was unclear when a vote would occur. The officials spoke on condition of anonymity because they weren't authorized to publicly discuss private negotiations.

The bipartisan 2002 No Child Left Behind law was a signature achievement of Bush, and its authors included the late Sen. Edward Kennedy, D-Mass., and current House Speaker John Boehner, R-Ohio. It sought to close significant gaps in the achievement of poor and minority students and their more affluent peers. It mandated annual testing in reading and math for students in grades three to eight and again in high school. Schools had to show student growth or face consequences.

But its requirement that all students be able to read and do math at grade level by 2014 proved elusive.

The Obama administration in 2012 began allowing waivers around some of the law's more stringent requirements if schools agreed to certain conditions, like using college- and career-ready standards such as Common Core. The standards have been adopted in more than 40 states and spell out what English and math skills students should master in each grade. They are a political issue in many states because they are viewed by critics as a federal effort even though they were developed by U.S. governors.

House Republican leaders used their bill as a way to show their opposition to the Obama administration's encouragement of the Common Core state standards because it prohibits the federal education secretary from demanding changes to state standards or imposing conditions on states in exchange for a waiver around federal law.

It also eliminates many federal programs, creates a single local grant program and allows public money to follow low-income children to different public schools.

Dan Holler, a spokesman for Heritage Action for America, said conservatives were upset that amendments weren't allowed on provisions their group supported that included allowing states to opt out of the law and allowing public money to follow low-income students to private schools.