I'm a first aid trainer. 30:2 is current guidance, where possible.
DD is a Brownie, and has just finished her first aid badge with her pack. She's 7. I'd already taught her CPR, and the recovery position about a year ago.
With CPR, both I and the Brownies taught her that it's not like the telly. Her CPR wasn't ever going to 'bring someone back', because that's not what it's for. We taught her that its there only to give the person a chance while an ambulance comes. We were also clear that it might not be enough, that not everyone can be saved, even in hospital but that she could help the give them their best chance and, in the end, that's all she was being asked to do.
We both also made it clear that the only thing she ever had to do was make sure an ambulance was called, whether by her or by someone else. And that her own safety always came first.
She was fine with all of it, and understood. She wasn't upset my any of it.
I, too, think it should be mandatory teaching in schools. Even if it's taught at 15 and never again, it still means it's not unfamiliar thing if, God forbid, it's ever needed.
I'm passionate about this, not because of the difference it makes - though it does - but because of a conversation I had with a former student once. His wife had a sudden cardiac issue at home one evening. He called for help and started CPR, but she sadly died. When he spoke to me, he thanked me for teaching him - not because it had worked, but because he felt he'd been able to do everything he could to help her, and that was worth a lot to him afterwards