Cheerleading question! (long Q!)?

No, the don't expect you to know everything on the first day! Is this class at a gymnastics gym? Most likely, they will just teach you tumbling skills such as back/front walkovers, back/front handsprings, etc. I'm naturally very inflexible, and at my tumbling class there's plenty of other girls that aren't flexible either. You can practice your flexibility at home. So don't worry! The whole point of a class is to learn new things, so they won't expect you to know how to do everything! Good luck! It's great that you're following your passion. Cheer is so much fun!