To me, the clearest way in which this is happening is through the federal government attaching conditions to the money that it gives to the states. This is not new, but it is still common.
A good example of this is the No Child Left Behind Law. This law did not tell states that they just plain had to do testing or anything else. Instead, it told them that they had to do those things if they wanted to keep getting federal aid. They were free to do what they wanted, but if they did not do what the federal government wanted, they would lose money. A similar thing is being done by the Obama administration which is giving states money for education in their "Race to the Top" only if the states do things the way that the administration thinks they should be done.