Fair enough, I was a little hasty to jump on that. I had been primed by coming from a discussion on reddit where they were calling the writer similar things because he is a moral realist. I was expecting another "moral realism is obviously stupid" response and that coloured my reading of your post. Yes, you have a fair point that these definitions have to be simplified as a teaching tool for young kids, so perhaps we shouldn't be taking them quite as an expression of the educators' deeply held philosophy. But it is so easy to tilt people's thinking by the way we frame the debate through terminology that I'm still a little wary of these definitions and of the exercise that requires children to decide whether something is an opinion or a fact. Such an exercise could be valuable as a way of starting a discussion but if it suggests to kids that this is a judgement we should be able to make just by looking at the statement, before engaging in debate about the statement's content, then that's an insidious pernicious effect.