I agree...please clarify. It sounds like your mom decided to enter you in some fence classes at a show and you don't know how to jump. If so--ack!--it's not as 'easy' as it looks. Now, if it's a cross-rail class, and your horse is trained to do trail, you might (emphasis on MIGHT) be okay. If not, I say scratch the class.
If, however, she signed you up for lessons, I say go for it. What you'll learn over fences will help you become a better rider. But I sure hope you'll be using a school horse. Some so-called trainers will put a beginning rider on an equally green horse (so they can learn together! Like...yeah, that makes sense!) The result is a disaster. Just take care.