Just throwing in my anecdata, used to be a late riser (often after ten), had a kid and now I wake up a bit after six. Sleeping in is after eight. I just have to

Just throwing in my anecdata, used to be a late riser (often after ten), had a kid and now I wake up a bit after six. Sleeping in is after eight. I just have to get up when he does. If I had to guess, I'd wonder if school conventionally starts early because pre-teens are up early.