Are trained adults unable to tell the difference between good teachers and bad, or are they merely unable to do anything about it?
When I was in high school, everybody -- the students, the parents, the administrators, and other teachers -- knew who the good teachers were and who the bad teachers were. But they had seniority and were protected by the union, so the school couldn't get rid of them; and since the school couldn't get rid of the bad teachers, they had to assign students blindly (since if students could pick which English 11 class they took, nobody would take the one with the lousy teacher).