@Panino
Too many students per teacher, too rigid a curriculum, standardized curriculum would only be able to discover certain types of talents and not others, and people in general have a tendency to not want to stand out from their peers.
These individually or in combination can make students achieve less than they could have in a better situation.
I've seen at least one real life example back when I was in school. A math talent who was afraid of standing out from her peers and so stayed in a class that was below her level. The teacher who didn't notice because she avoided answering his questions and he was stressed out from dealing with a troublemaker class all the time.
Another student I know was insanely talented in languages, but spent years being told he was dumb/bad at learning in school because the curriculum asked for different things than he had a talent for.
I also worked in schools for a little while and so was able to speak to (aka listen to the complaints of) alot of teachers. They felt that they weren't able to teach properly because of the emphasis on the curriculum and testing, too many students, and too little time to cover each section of the material.
Schools in different places will be better or worse, my point isn't that this way is bad/worse, because I don't think it is. Overall I think it is way better.
My point is that I can understand why he would say that some talents would be buried by this system.