They have three options,
Junior 1 k80 age 8-12, with the club Rick mentioned, with options for out of state racing, and the largest of the 3
Mini Max age 9-12, the fasest of the 3, with options for out of state racing
Junior 1 Honda age 8-12, runs in the CSC, class only run in CO but pulls decent numbers
At 12 is the transfer year between cadet or full size karts, they can go either way. Our shop (Shockwave Karting) runs karts in all 3 classes, call me at the shop and I can go over everything in detail with you.