Former President George W. Bush's education secretary, Margaret Spellings, has disclosed to a New York Times reporter why she has discontinued her role as an education adviser to candidate Mitt Romney's campaign.

"I have long supported and defended and believe in a muscular federal role on school accountability," she told The New York Times in an article published on Monday. "Vouchers and choice as the drivers of accountability; obviously that’s untried and untested."

In May, The Huffington Post's Joy Resmovits reported that Spellings chose not to remain with the campaign because of differences over federal accountability in enforcing the No Child Left Behind Act but that she still supports Romney.

Following her departure from her advisory role in late May, Spellings, an education policy strategist for the U.S. Chamber of Commerce, told EdWeek that Romney was "one of the best governors in the country on education." The Romney campaign listed her as an adviser in early March.

The Times reported that Romney never uses the hot-button word "voucher" to describe his education plan but would allow students to use federal funds to attend any school they choose.

Romney envisions a smaller federal role than what was envisioned by Bush in connection to the No Child Left Behind Act, which requires public schools to administer standardized tests. Romney advisers said he generally supports the law but would "replace federally mandated school interventions with a requirement that creates straightforward public report cards."

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