Banning cram schools isn't going to slow down overachievers. If anything it will allow them to do something more creative with their limited time than repeat the same kind of problems with a slight twist time after time to never make a mistake and gain that extra 0.1% of time efficiency to increase the amount of time to verify their answers at the gaokao.

If you're opposed to banning this on an ideological ideal of freedom that's one thing I certainly empathize with, but I honestly think this will greatly benefit overachievers at the relative détriment of middling students.