Karate & Tai Chi are both martial arts but are also very different. I think that tai chi is chinese and the movements are smooth and fluid while Karate has sharp movements and more pronounced thrusts and kicks. Plus there are belt advancements - I'm not sure there are belt colors in tai chi ?? I'm not an expert but it seems the two are different enough that it could be confusing for a child to learn both. Perhaps it is better to select one type or style of martial art at a time. ??

If your son proceeds with karate instead of tai chi, I'm sure that he will be able to learn tai chi later on should the opportunity present. You could keep offering to provide tai chi training from time to time in case .. although it sounds like it is very disappointing for you that your preference is not being seriously considered by your X. It seems to me that tai chi is least agression causing of all the martial arts out there and so her comment doesn't make any sense. Besides, I've never heard anything about martial arts CAUSING aggressive behavior but I have heard of martical arts helping a person control and channel aggression.

Perhaps you could get involved with the karate at the school and observe or help out. Maybe you can get tai chi into the class itself and thereby get the training for your son without ruffling any feathers.

Good luck