Need a good leg workout for a 13 year old boy. He plays baseball and he is the pitcher. His coach told him to strengthen his legs.

What would be a good leg workout to where he could still function at practice tommorow?

This is what I do for legs would it work just fine or what?

leg extensions(warm up) nice and slow-15,12,10
leg curls squeez at the top really hard-15,12,10
lunges-15,12,10
squats-15,12,10

Thanks for your help bro's it is much needed as always.
Brewski maruski