Through my years as a tennis professional, I have found a bounty of benefits in pairing a student's private lessons and group work with tennis specific physical training. After what we've seen over the last decade in professional tennis, its effectiveness should come as no surprise.
Anyone who watched this year's French Open listened while the commentators reviewed the changes in the training regimens of Dinara Safina, Svetlana Kuznetsova, Andy Murray and yes, Roger Federer. This all goes back to Ivan Lendl and Martina Navratilova adding training to gain dominance over their contemporaries.
There are many benefits in this type of training for juniors. Training sessions mirror points, games and sets in their duration. A group focus is achieved which makes the work easier and clears the mind. Players experience improved focus after these training sessions. Maintaining focus and controlling one's temper are so often deciding factors at the end of a long match. Mastery of focus and emotion is only achieved through vigorous training and play which tests a player in challenging conditions. In a majority of matches, the more physically fit player wins, both at the junior and professional level, so this training is vital.
Interestingly, beginners learn the game more quickly. They find the changing tempo of the game more easily and focus far better in this critical time where good habits are established.
Lastly, parents are often reporting that their children are more productive at school, more active after school and are less moody at home after training under this style.