Here's the message. As you can see, you don't need a race prepared car to attend.
--------------------------------------
"Our next Competition License school is scheduled for the next event on April 14&15 at Buttonwillow. At this point, we only have 4 entries and need at least 10 to run the school. As such, if you plan register to gain your provisional racing license please reply to socalinfo@drivenasa.com and let us know that you will be attending. Please reply no later than 3PM tomorrow so we can get an accurate count of who we should expect.
The competition school is hosted by www.drivingconcepts.com and you need to have participated in HPDE4 or Time Trials to qualify. A competition prepared car is NOT required and if you are thinking about joining the competition groups this is your chance to get into the school."