Street tires in the rain are for girls. My mostest favoritest track event was in the wet at VIR on Victoracers. I was really surprised at how much cornering grip they offered in the wet. High speeds in a straight line was actually the only thing that was a bit hairy - I limited myself to 85-90mph on the straights because the car was dancing around quite a bit. I was one of two AWD cars there, the other being an S4 that I passed like he was standing still.
When we went to line up for the 2nd or 3rd session of the 1st day my instructor told me "Make sure you line up early so you're at the front of the line. No point embarrassing everyone again."
Anyway, concur with BigSky's recommendation to soften up the suspension if you can. If you can follow in the tire tracks of the guy in front of you, you can catch the dry pavement they just squeegied for you. Not something you can do all the time, of course, but sometimes it works out. Really, the big thing is just to be as smooth as possible. Acceleration shouldn't be a problem, but braking, turn-in, and any mid-turn corrections need to be nice and easy. It really is a good way to learn, and can be a lot of fun.
'97 Legacy 2.5GT sedan