I've always wondered if he did this on purpose. I asked him recently but he doesn't remember, so there's a good chance that he just wanted to hack his stuff on his own :-)
But as I mentioned he is a teacher, so let's say he did this unconsciously.
Another thing that irks me about the Australian education system is how it's designed to create pacifists who aren't motivated to protect themselves. If another child in the playground hits you, you're meant to do nothing. That's not how to create a generation of people who can stand up for themselves.
My parents were very pissed off when they found out that's what I'd been taught at school. Sure, it makes life easier for teachers, but that's not the point of education. But it's probably a cultural thing, since my parents came from a country that was at war and that experience taught them how to protect themselves.