everyone fools themselves into thinking that they were much better than the students' previous teachers.
I'm friends with a couple of teachers--some of them are more excited about it than others, and those that are less excited aren't fooling themselves. I'd guess there's a large amount of sampling bias here, in that teachers who write about their problems and education policy tend to care more than teachers who don't. I would guess that that would lead them both to be better teachers AND to be more motivated to convince themselves they were better.
Did you read the original post? Does it match what you observe?
Post by fellow LW reader Razib Khan, who many here probably know from the gnxp site or perhaps from his debate with Eliezer.