Id give a grade of D
While the best students do well and Chinuch works great, for anyone average or CH’V less than average or at the bottom, they want nothing to do with them.
Anyone can make a good student into a Talmid Chacham. Good Chinuch turns a TERRIBLE student into a a Tzadik.
Rav Shlomo Freifeld went to Rav Hutner and asked for the 12 WORST learners in the yeshiva. And he made them into the leaders of today.