Yeah, I meant that you can't say it outside of the school. If you do, a typical reaction is: "If you don't like children, you are not a good teacher." Because it is assumed that if you like children, you would never say anything with a negative connotation; and if you don't like them, you are a psychopath and should be kept far away from them.

So, either the children are perfect, which means that if they don't get good grades, you are a bad teacher; or you disagree that the children are perfect, which proves that you are a bad teacher. -- The only way to signal that you are a good teacher, is to give best grades to everyone. Some teachers use this strategy, knowingly or not.