The mass exodus from President Bush's signature education overhaul continues: Eight more states have applied for, and been granted, waivers exempting them from a testing requirement central to No Child Left Behind.

Signed into law in 2001, No Child Left Behind attempts to hold schools accountable by requiring them to demonstrate steadily rising student progress or face penalties. Educators have complained that the testing mandate is too rigid, and a requirement that every student become proficient on math and science exams by 2014 is widely regarded as unattainable.

The news of a fresh round of waivers comes soon after Republican presidential nominee Mitt Romney delivered his first major speech on education policy, emphasizing an issue that has been largely absent in the presidential race so far.

Congress has been unable to agree on a rewrite of No Child Left Behind (the law is itself a renewal of the 1965 Elementary and Secondary Education Act, the foundation of the federal government's role in education), so President Obama has preempted a legislative fix by offering states waivers that free them from the 100 percent proficiency target.

States seeking those waivers must offer plans to implement a number of the Obama administration's school reform priorities, including formulating career and college readiness standards, and, more contentiously, crafting teacher evaluation systems that incorporate student testing data and can be used to fire or reward teachers.

With the latest round of waivers, a total of 34 states have now opted out. The latest eight states to leave are Connecticut, Delaware, Louisiana, Maryland, New York, North Carolina, Ohio and Rhode Island.

While Romney has cautiously praised No Child Left Behind for raising standards and bolstering schools' ability to gather data, he has also advocated stripping out the law's heart. Rather than have faltering schools face punishments that include replacing staff or converting to charter schools, Romney said he would have states publish report cards assigning schools an A through F letter grade.

Education has yet to play a notable role in this presidential election, but Romney brought the issue to the forefront last week with a policy speech declaring a national education emergency. Romney charged that President Obama is too wedded to teachers' unions to back serious education reforms.

But while it is true that teachers' unions remain a reliable and formidable reservoir of support, the Obama administration has aggressively pursued policies that teachers' unions object to. The president has offered states incentives to raise caps on charter schools, embracing a longstanding Republican tenet of encouraging school choice amid accusations that he is undercutting public schools. 

Republicans often portray teachers' unions as protectors of entrenched interests, willing to put their members' job security above the children they are tasked with helping. But by pushing states to implement systems that grade teachers and then link those scores to decisions about which teachers get promotions or get dismissed, Obama has backed a school reform measure that teachers' unions consistently reject.

President Obama has done so by dangling rewards in front of states. The criteria for getting a No Child Left Behind waiver and for competing in a program called Race to the Top, in which schools seek federal education dollars by offering reform proposals, reflect the administration's education agenda.

While that record belies Romney's criticism that Obama has been unwilling to act on education, it could play into a common Republican critique that Obama is overreaching. Lawmakers objected to the president's decision to offer states No Child Left Behind waivers, charging that the president was abusing his powers by overriding Congress.

Still, many of the buzzwords Romney invoked in his speech -- from school choice to regularly evaluate teachers for their effectiveness -- do little to distinguish him from his opponent.

The main point of departure was when Romney advocated taking the money that flows to school districts based on how many low-income or special needs students they have and having that money follow each child instead. Essentially, Romney was talking about a voucher system: Rather than the money going to a public school system, it would go to a student who could use the funds to attend a school of his or her choice.