There seems to be this mantra that cycle helmets are the first and last thing with bicycle safety. Lots of schools won't let you ride to school if you don't wear a helmet. They don't give a shit if the bike has functioning brakes, or the fork is the wrong way round (both pretty common faults), but they'll go crazy if a child comes in with no helmet.
Here's a video:
Young boy, nearly gets killed by a lorry. He obviously has no idea about safe riding. His parents have bought him a helmet, he's wearing it even, and it looks like reflectors on his trousers as well. So they obviously are concerned about his safety on his bike.
But his riding style is incredibly dangerous. And this kind of riding is pretty common.
If you get run over by a lorry, a helmet will do fuck all for you.
There is a regular stream of teenagers who get killed riding on roads.
AIBU to think that the idea that you just buy your child a helmet and it's off he goes, is actively dangerous, and that the first priority should not be 'are you wearing a helmet?' but 'Can you ride safely?' (which in this case would either be a shoulder check and hand signal, or simply crossing the road on foot at a gap in the traffic.)