There are 6 or 7 (depending on who you ask) key movement patterns to train with a young athlete. And he most important thing is to make them strong and technically efficient in those patterns.
The basic 6 patterns are:
And to that some add a 7th one: unilateral leg movements.
Now each pattern has exercises of various levels of difficulty. And much like school you don't skip to a more advanced "grade" before you have mastered the preceding one.
Level 1 - goblet squat, KB squat, DB (one in each hand) squat
Level 2 - Front squat
Level 3 - Back squat
Level 1 - Romanian deadlift
Level 2 - Deadlift
Level 3 - Power clean from hang, power snatch from hang, KB swing
Level 4* - Power clean from floor, power snatch from floor
* This level is no necessary to reach a the early high school level
Level 1 - Push ups (don't laugh most don't do them properly)
Level 2 - Bench press, incline bench press
Level 3 - DB bench press, incline DB press
Level 1 - Military press
Level 2 - Push press
Level 3 - Power or split jerks
Level 1 - Seated row on pulley station
Level 2 - Bent over barbell row (the ahlete must first master the Romanian deadlift and deadlift)
Level 3 - Ring row/invered row eventually shooting to do them torso parallel to he floor by elevating feet
Level 1 - La pulldown on pulley station
Level 2 - Assisted pull-ups
Level 3 - Pull-ups
UNILATERAL LOWER BODY
Level 1 - Split squat, Bulgarian split squat
Level 2 - Backward static lunge, forward static lunge
Level 3 - Backward walking lunge, forward walking lunge
The key is not to skip step just because you want to add some lifts that are popular in college and pro programs. It's better to stick to the lower levels longer and really hammer in perfect position and technique.