Actually, as I recall from Stein's earlier American Spectator articles, the kid is not a good student. Stein often mentioned how he had to beg and badger the kid into doing his homework and working at getting good grades. Stein mentioned many times about how the brat would spend hours playing his video games, (eagerly purchased by dad).
The old standby, "he's really smart but just won't apply himself" seems to be the nominal excuse.