Just back from half term with family in USA.
Where they live 15 year olds can drive (!) due to crap local transport.
15 year old DN has been driving to school, around town etc for 6+ months and was apparently excited to get to take my kids (10 and 12) out in the car to the local coffee place a few miles away. On their own.
Now - if they were walking I would have let the 3 get on with it, go out together but there was NO WAY I was letting them go out in a SUV in a city on their own.
Had a quiet word with the mom to that effect. Everyone thought I was the ultimate buzzkill and a bit insulting to the 15 year old. my offer to go with them was shot down. The trip didn’t happen.
YABU - fun police! It would have been fine and the 15 year old would have been able to handle it sensibly.
YANBU - 15 is too young to be responsible for young passengers, too young to be in the roads alone in fact.