Oh, I guess my post was directed at you then.
So why do you think it necessary for a person to have done a thing in order to criticize a thing. I mean, I think it's funny that people who have never been President criticize the President, as they clearly don't understand the pressures involved. It's strange how people criticize rapists. If you've never been a rapist, you don't know the pull and the magic that it contains for a rapist. Etc.
Nobody has to be an expert on teachers in order to say: I don't know about you, but many of my teachers weren't worth the paper their various certificates were printed on.
This idea that any criticism of teachers is invalid because it is made by people who haven't taught, or done research, is a pretty cheap argumentative tactic. I did 13 years of research by being a student who went to school every day and realized: Hey, this is a major problem. Most of these teachers don't seem like they care about what they're doing.
Students generally don't succeed because of teachers: those who have special success usually would have had it regardless of who their teachers happened to be, because they were curious people who were interested in learning and willing to do the work. College shows us this. But, heaven knows many teachers are quick to point the finger at parents when a student isn't succeeding.
So, do teachers deserve the credit but not the blame?
My own opinion is, they don't necessarily deserve the blame except in certain extreme cases where the teacher is a real dickgoblin. Many of us had at least one such teacher. (For references, see the Pink Floyd song, "Another Brick in the Wall, Pt. 2.") By the same token, they don't usually deserve the credit except in certain extreme cases. (See: your favorite teacher.)
So what I propose is: let's not be so impressed with teachers.