I am signed up for Perfomance Driving Clinic in December. ( car racing)
http://www.buttonwillowraceway.com/

However my own car is not suitable to race.
Question - what is a good make model for racing that can be rented for
a reasonable price.  Rental Corvettes are too expensive, $1000 per day
and all are convertibles.

I would postpone the School until you have the car that you plan to
race. You'd get the greatest benefit for the dollar that way. If you
are going to race anything, I'd start with the Vintage Racing classes
that have sprung up in the last 20 years. You buy an old racer from
the 1950's thru 1980's and have some fun. The safety rules are usually
as strict but the allowed modifications are a lot looser. Parts and
cars are cheaper. good luck.

also, you can start to do formula vee. formula vee is a class of
racers built from donor air cooled volkswagon parts (old Beetle,
Karmann Ghia) with arodynamic bodies. this class puts more emphasis on
driving ability rather than car abilities. plus the cars are cheaper.

a good resource is here
http://www.fvee.org.au/about.html

but you can look into it more for the us in various VW magazines.