An old car. Or an old truck. Like this 1954 F100. No power steering. 3 speed manual transmission. Straight 6, maybe 115 hp. 4.27 gears, you won't go much more than 55. Nor would you want to with the king pin front suspension. Drum brakes with no "power." No radio. No lighter. No back seat.
There is nothing to distract you from the driving EXCEPT for the driving. It takes two hands, two eyes, two ears, two feet, and a brain to operate. There is no time for even a quick text; you're either trying to fit it in the right gear, working the wheel to stay between the lines, or both. Apart from a hands-free device you won't be taking or receiving calls, it's two hands on the wheel or one hand on the wheel and one on the shifter....and even with it you'll be having fun talking over that bad ass tractor motor. No radio to fiddle with. It's an all immersive, all hands on deck, keep your head in the game driving experience.
I'm 35. My generation still mostly learned on manual transmission cars. We had radios, but nobody had mobile phones. Not to sound like Walt Kowalski, but today's kids have iPhones before they're in junior high. On one hand that gives them a head start on walking and chewing gum at the same time, on the other hand not many teens will truly get the "man and 4-wheel machine" experience I got as a 15-19 year old.
There are some, you know, flaws with this idea. My '54 doesn't have airbags. Or seat belts for that matter. It wasn't designed "safety first." Admittedly those are, potentially literally, fatal flaws. It's far fetched and probably not realistic, but why can't we build "starter" cars? Stripper late model cars with today's safety advantages and yesteryear's demand for the driver's attention. I hate to add more laws and layers of regulations, but learning to drive a car built in this manner will be safer in the shorter term and make a generation of better drivers in the long term.
Obviously some parents do this sort of thing when searching out a starter car, but others just want a "safe" rated vehicle, ignoring the fact that their kid will just put it in autopilot and use it as a mobile entertainment system. Safe for your kid, not necessarily for the people on the other end of a 4,500lb missile.
Bored old man rant off.