We're out in the country, so I started them at age 13 on rural roads, and at age 12 on off-road bikes.
I told them "I've got 500,000+ miles driving in a car over the last 40 years, and I've never dented a fender, been in a collision, or had any kind of incident.
"You're going to drive just like me. You're going to accelerate like I accelerate, cruise at the speeds I cruise at, brake like I brake, take the line through turns that I take, follow at the distances I follow. If I'm riding with you, and my foot reflexively goes for the brake because you didn't start braking when I would have started braking, then I'm taking over the wheel."
It's working. They've been driving now for 16 and 18 years, and neither of THEM has ever dented a fender or been hit by a car ....
Like they say, it's not bragging if you actually do it ... !