My son is 9 years old. He turns 10 next summer. He is 5ft tall and moves reasonably well. He plays a lot of tennis and loves playing in tournaments. His footwork is the area that needs the most improvement. He works hard on the court and has his feet moving most of the time. Also, he could get a little stronger. How much at this age is appropriate when working on these areas. I am sure it is easy to do too much which could lead to injuries. Also, what would you recommend? I am sure there are some things that he could do that I am unaware of. Right now he does clinic two days a week, 30 min lesson on another day, and usually plays tennis on one or two more days.