Numerous vocal critics oppose No Child Left Behind. Criticism of NCLBA typically falls into three different categories. First, as with ESEA, critics charge that NCLBA causes the federal government to intrude too much into what has traditionally been the domain of the states. Second, opponents contend that NCLBA has resulted in unfunded federal mandates, which essentially passes financial problems from the federal government to state and local governments. Finally, detractors allege that the law places too much emphasis on standardized testing and stringent teacher qualifications.

Speaking on behalf of its 2.7 million members, the National Education Association (NEA) is an outspoken opponent of the law. The NEA argues that NCLBA requires stringent accountability, but does not provide adequate funding necessary for schools to meet those requirements. The NEA also claims that NCLBA punishes schools rather than providing assistance, and that it promotes privatization of education.