@MDRI - If your son wants to get into a highly selective program, he should try to improve his General GRE scores. Taking some practice exams might help. As for the PGRE, it is really useful to look at a practice exam and figure out a good strategy for taking it. It is unwise to try to work out the problems on this exam. There are just too many problems to be able to do this.
I agree that he should speak with his mentors to identify programs he would be able to get into. This is the kind of discussion I have with my advisees all the time.