I am not sure why this topic struck a chord -- perhaps because I was a car-free teen all through high school (SF Bay Area) and used my Coast-to-Coast ( a hardware store when I was a kid ) three-speed with wire-rack panniers to get around. That bike never had an ounce of panache or sex appeal: it was a butt-ugly work dog. I hated it. But it got me around, and some surprisingly large distances at that.
If I were a teenager today (I am fifty-three) I would try to stay car free as long as possible. Cycle, ride the bus, bum rides, be creative. But **save** all the money you would have spent on gas and insurance and maybe the cost of the car itself or the payments, and maybe a few extra hundred a year on top of that for maintenance, and the price of new tabs every year too. The money is staggering. If you save it, you can use it for college, or to cycle through Europe or Canada or the USA or whatever.
FWIW. I wish I had.
