Legally, they can teach that. It's not disallowing a child to do this, it's advising them not to. I see nothing wrong with the school system trying to keep children safe on the internet... These rules may seem extreme, but they're obviously directed to children with less common sense. So yeah, while you proceed to ramble about how dumb these rules are, think of the large amount of naive children who have been taken advantage of online. At least the people who made this list are trying to do something about it.