I can't even tell you how many of my guys come in for a session because their mom is making them do it. Most (if not all) leave the experience with a smile on their face and a feeling that they are so glad they did it.
These sessions are to give Mom some beautiful photos of you, sure, but they are also a chance for you to express WHO YOU REALLY ARE at this time in your life. There is a reason you hear old people talk about their high schools days. This is a time YOU WILL NEVER FORGET. Stories of your senior year will live on in infamy. Shouldn't you have some great photos to help you tell these stories to your kids someday (well, some of the stories anyway ;-)