The answer to this depends largely on one’s political point of view.
From a strictly legal standpoint, the federal government’s educational policies are perfectly constitutional. The federal government does not simply tell states what to do in terms of education. Instead, it tells them that they can have federal assistance if they do certain things (such as those ordered by the No Child Left Behind law) that the federal government wants done. Therefore, the states are voluntarily complying with federal guidelines and there is no constitutional problem.
Some people, however, would argue that this whole process is incompatible with federalism. To them, the states should retain much more power than they do now. These people would like to see the federal government stay out of areas that are not expressly delegated to it in the Constitution. To them, the use of federal taxing and spending powers to impose educational policies on the states (as in the No Child Left Behind law) is a way of subverting the spirit of the Constitution while adhering to its letter.
Thus, there is no legal problem with the federal government’s educational policies. However, there are those who feel these policies are contrary to the spirit of the Constitution’s federal system.