In other words, the reason why Japanese students have to study so hard for the "juuken" is not because it is that hard, but because they didn't know their real ability due to the lack of real eliminatory exams before that. As a results, many simply do not have the necessary knowledge and instead of "doubling" a normal school year like in Europe, they end up becoming "rounin" and study one or two more years by themselves or at a "yobiko" (preparatory school) to be able to enter university.
I think this is the mayor problem in Japan, you just learn "little" so to speak, and for entrance at a university the Japanese have to LEARN(not memorize like they did before) and that's something they never really learned so they will go completely COOCKOO !!