i tracked my mazdaspeed3 and it has some potential - although it is not a trivial car to get going really fast and there is not much you can do once you reach the limits of FWD (although for a new driver that could take quite some time). Pretty frustating to sit on 260hp coming around the corner and having to wait so long to put all of it down.
on the plus side, does great in the snow/ice (with right tires of course) or on the wet track and very practical (fits 4 viper wheels/tires in the back with room to spare - think of the possibilities...). if you can score a set of FD RX7 16" wheels, you can have a killer (and cheap) setup for the track or for much more comfortable daily driving than the stock 18s.
subaru idea is OK too, as long as you get the one from before they started to stuff them full of fancy computers
edit: here's another idea - 3 series coupe - e46 or even e36.
You get a light(er), track proven RWD platform, capable to deal with any weather with the right tires, plenty of power to learn to manage it (esp. if you go with 330), but not enough to mask bad habits. I know a couple of drivers who are very fast in these with only minor modifications (camber plates and tires, basically), so the potential to reward good skill development with lap times and wave-bys from 911s is certainly there, if you know what i mean.
I would actually argue for RWD in the winter (again, with the right tires) for newer drivers mostly for educational reasons. Your kid may feel like he is in survival mode on his first few snow days, but it will pay off in the long run. Better to go through owning RWD car in the winter as a choice, as opposed to finding yourself in a low traction situation in RWD car one day and no experience to fall back on.
Also, in my opinion, 3 series is a better skill development platform than something like a WRX subaru, mostly because input/feedback connection is very direct and predictable, almost like in a miata.
final thought: do NOT get anything with weight/power ratio under 10 or so as his first track car. if he is competitive type and wants to get around porsches and corvettes at the local DE event, let him learn how to do it using all of the car instead of just the go pedal. i made that mistake with my first track car and spent several years unlearning bad habits and quite a few dollars fixing the consequences. i know, silly point to make on the viper forums, right?