For a legitimate box jump, the hips must travel at least as high as when standing on the box.

Strength
Back Squat
5-3-1-1-1 reps
 

WOD
21-18-15-12-9-6-3 reps of the triplet:
Front Squats (75/55)
Push Press (75/55)
Supine Ring Rows

 
Rx+ = use 95/65 for Front Squats/Push Presses