While I don't know if it happens in schools, taking pictures of strangers is considered a really offensive, intrusive act by the Japanese. While I was sightseeing in Akiba, my Japanese host cautioned me not to take a picture of a girl wearing a maid outfit while handing out flyers for a maid cafe. She implied in the usual roundabout way that it wasn't acceptable and could be troublesome (how, I'm not sure and my host didn't elaborate).