The video is from a dash cam in a lorry. Lorries are big. It is therefore plausible that the overtaking driver didn't see the school bus until it was too late; because it was obscured by the lorry.

Having rules about what kinds of vehicles you are allowed to overtake seems imprudent. "I'm not allowed to overtake school busses" isn't a question they're going to ask themselves often, because overtaking shouldn't have to happen often, and even when it does, only sometimes will it be a school bus. Easily forgotten.

Meanwhile, in the UK, schoolchildren get back home just fine without special rules about overtaking busses. It's just generally accepted that you shouldn't be an idiot when overtaking a stopped vehicle by disregarding the fact that at any given moment someone could walk out from behind it; and it's also generally accepted that you shouldn't just jump out into the road from behind a stopped vehicle.