Teachers
I currently study teaching, and even though i hate having to justify myself in this way, I got the marks to do law and a number of relatively highly renumerated careers (shock horror).
Why didn't I? Well, you could just as easily ask why I didn't do radiography, Sinhalese, or gender studies.
Undoubtedly, there are some teachers who do very little work. But what industry doesn't have those people?
Basically, don't undermine your intelligence (which teachers undoubtedly helped to foster) by making generalisations. Even though you may have spent upwards of thirteen years in the classroom as a student, the experience on the other side of the desk is totally different to many commonly held perceptions.