Jim , as Demick has pointed out CDS or GGR have some great ways to improve your performance driving skills.
I suggest you avail yourself of what these groups have to offer before you look into the expensive schools.
I have instructed in GGR for ~15 years now and have also instructed with CDS.
Both groups are Porsche centric. You will get instruction from fellow Porsche drivers who are some of the best incar instructors on the west coast....Period!
Much cheaper than Russel etc.
I have had many students over the years tell me they got more from a day with a GGR event than one of the private (expensive) schools.
You will be instructed in your car, not some openwheel Formula Ford, or Dodge Neon etc.
You can get to any GGr AX and get good instruction or go for a GGR HSDS and receive instruction all day on the track.
Next step would be CDS for a little more freedom.
Next would be back to GGR for Time trial. Instruction is available or mandatory at all of these events. (depending on your skill and event)