There are schools that have have bikes from 125cc to 1200cc; however, those school are more spensive to go. I think they are like $2000+ bucks. In that school you can have 6Rs, R6, CBRs, etc. The MSF school is supposed to teach you the basics only. For someone to teach you the basics on how to ride a motorcycle doesn't need a 600cc. Just imaging how spensive it is for them to maintain a 600. Furthermore, how much is going to cost them when people dropped them. By having smaller bikes a person can feel more confident and comfortable, and it is easier to ride it 2. Plus people won't feel intimidated by the size of the bike either. You will be surprice on how people can't ride a 125cc because they do not have throttle or clutch control. More to it, just imagine yourself on a 600cc bike and it is ur 1st time riding it. You won't feel confident on turning at slow speeds because you are going to feel like the bike wants to go down. With a smaller bike you can stop that from happening becasue it is not that heavy. After you have mastered all the basic (which takes a lot of practice by the way), then you can go ahead and get whatever you feel comfortable riding.