Nope. SS = super stock. FAST cars. Below that are AS, BS, CS, DS, ES, FS, GS, HS... and I think that's it. Some of them aren't really popular (CS, FS) some are. And I thought the 240 was moved to ES last year? (I've gotten that confused a couple times last year, leading to registration nightmares
).
Go to the moutons site (search yahoo for moutons and scca) and there is a basic listing of the classes. Gererally _S = (stock) stock except w/ shocks, tires, and brake pads open; STS (street touring street tire) = springs/shocks, limited wheels, street tires, I/H/E; _SP (Street Prepared) = STS + internal engine mods, iirc brakes open, iirc tires open - these cars get fast and $$$; _M (Mod) = SP rules + motor swaps; _P (prepared) = about anything goes w/n certain weight and power limits. I think that's the basics, but the moutons site will be better.