My thinking goes along Diana's. The best teacher in the state might not be the best teacher for your son Willa, maybe not at this point. My kids went through several teachers, the one that they are taking from now is supposed to be "superior" (if not the best in state than for sure in the best 2) but she is also extremely strict and sets very high expectations for all her students, no matter what age and how advanced.
Talk to this teacher, maybe he will have suggestions?
Ania