[LarryMullins]

It's an easy pretzel for teachers/school administrators to tie themselves into, because these people are on the frontline of witnessing the ways in which parents can neglect and abuse their kids. It's easy for teachers to fall into believing themselves / the state a better steward of children than their own parents.

[jbm]

I'm not sure if that is the case, but if it is, it is the educational equivalent of the police seeing everyone as a threat because they deal constantly with the law breakers of society.

[LarryMullins]

It's not a perfect analogy, but I think it's very similar. Teachers have to interact with all students, not just the ones who have trouble, but the ones who have trouble occupy a greater portion of the attention of teachers. So teachers spend an inordinate amount of time dwelling on the matter of neglect and abuse. The saddest most depressing cases stay in the minds of teachers for a long time, while the normal well cared for students are soon forgotten.