<<Maybe a few voices will. But with NCLB, does he even have a choice? Aren't his hands tied?>>
Maybe, there may even be a chance that he gave the grade levels guidelines on how to structure their day. I think principals are pretty stresssed over NCLB too, they would probably be the first ones to go if the school did not get accredidation. Which really sucks too. The main problem with the public school system is there are WAY to many politicians sticking their noses in it and trying to run a classroom like a business, and they haven't got a CLUE about what is best for the children. If it was left up to the teachers, test scores would probably be up, simply because they could teach in a way that children enjoy. (enough of my soapbox, though)
Did you ask his teacher anything about it? Did she act like she thought that 20 minutes was long enough? (even if it was ordered from higher up, I would have a hard time acting like I was ok with it when I told parents. KWIM?
You're son has started back, right? Has he said anything about the amount of time that they have to sit and do work, maybe she actually has them doing activities or something (trying to think positively, here). I would ask him about it and see what he thinks too.