Our 12 year old has been driving for over a year. I taught her on a standard transmission, an old beater. She drives around the farm and never, ever, on the street.
I took her out in the middle of a field and told her to close her eyes. To "feel" the clutch. She is really good at feathering it and doesn't hop anymore. That old beater is gone now though. She's driving the truck and the car and the van. I don't think she's gone over 10 mph either.
Our insurance said uninsured insurance will cover any accident she has. Since it's Oklahoma and on a farm it's okay. Still, I wouldn't teach a friends kid. I'd expect them to teach their own family.
If a friend of mine wanted to come to my house, in their own vehicle, and they had insurance then I'd probably do it. But not in my own vehicle.