I agree this is sad. On the other hand however one needs to consider how much is really lost this way.

Given the inefficiency/pointlessness of much of the effort involved in compulsory education, I'm not sure better teachers would be able to significantly improve the system. We need a structural change here first, and only then start to look around for brigther people. Otherwise, any bright people that may enter the system, will eventually be frustrated, give up, and in the end achieve results (in the field) that are no better than those of the borderline-acceptable teachers.