piano lesson nightmares

Both my boys are taking piano lessons and our piano teacher is a friend who is a wonderful musician but an impatient teacher. I've always thought this was OK because R. and W. need someone to light a fire under them. But our piano lessons are torture so sometimes I wonder whether they should be taking lessons or at least taking lessons with this teacher.
R. has to be poked and prodded to practice and I have to sit with him and I have to remind him to count. So he's not really taking responsibility for practicing himself. When I try to talk to him about it he says he doesn't want to stop lessons. If I force the issue, he says that he wants to play but he doesn't want to practice. This is what everybody says about piano. But I sympathize.
W. has no trouble practicing. He's such a go-go kid, he's always looking for something to do anyway. So W. is moving ahead and, in fact, is now in R's piano book even though he started several months after R.
T., their piano teacher, says that R. starts playing and then when he tries to correct him, he falls apart and loses energy and just seems to space out. Is this a reaction to T. yelling at him? I don't know. I know part of it is a function of R.'s ADHD. He just has tremendous difficulty concentrating and we're going to see his pediatrician tomorrow to see if we should increase his medicine. Meanwhile, I guess we'll keep soldiering on and see if things improve. I sometimes wonder if it's worth it or if we should be switching teachers despite my friendship with T. Sigh.