SAME situation with my CPIMO the most important thing is the quality of instruction. I don't think 4 is too young, as long as they are being taught proper technique and move through the levels appropriately. The first gym we were at did not teach proper technique for tumbling or stunting and my kids have struggled to re-learn skills, and some tumbling skills aren't even possible for them to do (i.e. Arabian) without relearning their roundoff.