They should applaud him
Kid decides instead of doing all the usual anti-social things teenagers get blamed for he makes, polished, popular videos and shares them with the world. The school should be applauding him, not punishing him. I hope they get sued. The fact that it's not to their taste is irrelevant (hint: it wasn't made for them, or given to them, or associated with them)
And AFAIK schools in the UK aren't legally in loco parentis, they are considered responsible for them, which actually makes things harder (i.e., in the event an accident it is there legal duty to ensure they have a way to contact the parents or those actually in loco parentis to make decisions)