You may feel like everyones watching, and you might even feel embarrassed that your not jumping as high as others, but its not the height of the jump its how you jump it, so i would say do eigther a cross pole class, or the 1ft class. Depending on how fit he is, you could do both of these classes and see how he is, then the next show you do, do the 1ft class to get him warmed up properly and get him used to this experience with you. And then after that class do the next class up and slowly through out the year build him up and get higher and higher to height he can handle, if this makes sence, sorry if it dont :)