But in many American suburbs, car is the only feasible way to get somewhere. So unless the 12-year-olds are driving, it's got to be the parents.
Do note my source is only a single colleague from CA, could of course be an exception..
My kid could definitely bike to school when she gets older. But to get to, say, her gymnastics class, it's 8 miles through heavy traffic with only occasional bike lanes. (In the dark in the rain, at this time of year.)