Potential location: Swing box
Like a mirror
Projects the shot you just took, and superimposes that on the image of someone hitting the ideal tennis shot.
This turns swing box into almost a batting cage -
For the overlay (hitting the ball to the camera) requires that the ball comes from the same place every time and requires the player to stand in a specific place.
If the camera is to the side (left or right of the student):
A la Dartfish