All kids are different, so it really bugs me when people generalize and assume they know about all children based on their experiences with children. Children do develop at different rates and do have different levels of understanding. For some children, it may be entirely appropriate to start gymnastics early. There may be others for whom it will never be a good fit. There's no reason to laugh, or assume that you know more about their child's level of physical and emotional development than they do. I have 3 supposedly normal children, one thrived on structure at 3, one that's 10 that I fear may never be able to cope with structure, and a third who is in the middle.