The department said Washington and Wisconsin received waivers from meeting the goal of making all students proficient in reading and math by 2014, raising to 26 the number of states relieved from meeting the centerpiece of the legislation passed during George W. Bush's presidency.
Waiver requests are pending in 10 states and the District of Columbia, while 14 states have not applied for them.
Because more than half of the states have received waivers, observers question whether the law is, in effect, nullified, The New York Times reported.
"The more waivers there are, the less there really is a law, right?" asked Andy Porter, dean of the University of Pennsylvania's Graduate School of Education.
No Child Left Behind has been praised for forcing schools to be more accountable for educating minority students and students from poor families, but it also has been criticized for its reliance on test scores and for its rating system that classified so many schools as low performing it made the system meaningless.
In exchange for the education waivers, schools and districts must pledge to set new targets for preparing students for post-secondary education and careers. They must also link school and teacher evaluations, in part, to student achievement on standardized tests and focus on troubled schools.
Congress has tried unsuccessfully to reauthorize the education law during the last five years.
Education Secretary Arne Duncan told the Times states receiving waivers would use a mix of indicators to evaluate teachers and schools.
Education officials in the states that received waivers said they were relieved about not having to meet the 2014 deadline.
"There was a general feeling that there were these goals that no one was ever going to meet," Kelli Gauthier, spokeswoman for the Tennessee Department of Education, told the Times. "Now we have standards that are possible."
A practical effect is that waivers remove many schools from being labeled as having failed to make what No Child Left Behind determined to be "adequate yearly progress" in getting more students to pass standardized tests. During the 2010-2011 school year, nearly half of the schools nationwide missed their targets.
"To label an improving school a failure is the worst thing you can do," Duncan told the Times. "If they're doing the hard work to get better, it's like, 'Why are we killing ourselves to improve if we're going to get slapped in the face for it?'"