There are so many things people have tried with a racing school.... but have they ever succeeded? So many ideas, and so much time involved to teach people something (especially ONE trainee), there are just too many drivers to go around that need help with driving.
To be honest, I see the best way of learning by self-practice and just instructional videos. I know some people have made videos, and they were instructional at best, but not very complete for any particular area of teaching.
There is lots to cover when it comes to training, and videos are easiest for everyone. Don't waste time and energy on trying to do live instruction with other drivers, it is just too difficult. Drivers need to learn on their own time, in Singleplayer/Hotlapping to become a consistent driver, as well practice with a medium-sized grid online. Because there are so many situations in racing that you just CANNOT do by "simulation" on your own server. You have to put a driver into the mess of racing and let them learn from there. Real driving schools do this a lot... just countless free-for-all runs. Though they do also tune 2 of the same cars, with one being a bit slower so they can practice overtaking.
Also, to learn, you need to make sure you teach people not to choose ONE car to "love". Players need to try new things so they understand all kinds of cartypes and how they go about controlling them. Otherwise, they will just be a typical amateur that only chooses one car (eg FOX), and cannot even drive an XRG quick enough.
Best way I learned back in S1 was by choosing a car that was the hardest and most difficult. The LX6. I stuck with learning that car for months on end, all by myself, up until I got my first World Record, I knew the practice had payed off. Then I went and beat one of Flotch's RB4 rally records on my first couple tries. It shocked me, but I knew I was getting faster. Then the MRT came out, and that was a very good training tool for racing side-by-side online. I'd choose a program such as this... Start with a hard car a driver dislikes using, become fast in it, try it online against other drivers..., then start with a new car.