The American T'ai Chi Associates recommends looking for a school that adheres to the original principles of the martial art it offers, rather than one that dilutes them by, say, pairing jujitsu with kickboxing: The purer the teaching, the more your child stands to gain.
The mean calories burned per minute of tennis, based on the list of 5 activities, shown below, for an average male, weighing 190 pounds (86 kg) is 9 Calories per minute. The average per minute for an average female, weighing 163 pounds (74 kg) is 7 Calories per minute.
These tennis activities range from the highest calorie burn from 'tennis, general' which burns 315 calories in 30 minutes through to the activity 'tennis, doubles' which has the lowest calorie burn of 194 calories in 30 minutes, for a typical adult weighing 190 pounds (86 Kg).