I've read quite a few times that the average age is 14 or 15. I really started cutting when I was 16, but I did stuff like hit myself, bang my head against things, and throw myself against walls or furniture when I was little.... I mean, it hurt, but I seldom got more than a few scratches and bruises and broken property from that. I guess in hindsight, maybe that was abnormal, but I've always thought it wasn't a very big deal without blood... As you can tell, lots of people start later, or maybe even during elementary school.