I understand why you would tell him not to throw the first strike, but I'm not sure I'd agree. If he lets the bully throw the first strike and gets knocked down, which is a real possibility, he could be literally or effectively out before he engages his training, and that's too late. All the axe kicks, hook kicks and katas won't help him if he's allowed himself to get pinned by someone much bigger and stronger. Obviously I don't know what he's taught or what the sensei might be willing to teach him if asked, but what I've been trained to do (in a course designed for adults) is to see the warning signs - aggressive language, "big-dogging", ie: chest and chin out, showing who the bigger dog is, and respond by creating a "fence" with the hands, not a guard or anything aggressive, just a way of indicating where one's personal space is, if the attacker hits that once, back away and try to talk him out of it, if he hits it again, ask a question while subtly "loading up" the dominant side, then when his brain is engaged to deal with the question, smash him and don't stop until the threat is removed. It might be worth asking the school what he's allowed to do in self defence and if they have specific rules about what situations he's allowed to do that in. I would be surprised if they tell you he has to let the bully strike first if he's being threatened.