Anytime. Other things...
I don't know his HS coach, but as Art stated, do not think his coach's program is any better than what he's doing now. I might even state, with the increases he's seen during non-season, that's evidence it's not as optimal. Unfortunately, telling a HS football coach he doesn't know shi'ite doesn't bode well for playing time.
Is he squatting first in the workout? It's taxing, so once he's warmed up it should be go-time on the squat. An example of a warmup I would do, coaching someone squatting 275, would be the following:
3 sets of 5 reps, just the bar.
1 x 5, 95
1 x 5, 135
1 x 2, 185
Minute rest
1 at 225.
2 minute rest.
3 sets of 5 reps x 275
4 minute rest between each set.
I think if you follow this approach, add 5 lbs to each workout set and he'll keep that up through probably 315. Add another warmup rep at the midpoint weight once he's maxing at 285 (so 255 there, or if maxing at 305 the midpoint would be 265).
He needs a belt. Up to him if he gets lifting shoes, but I see movement in his feet in his current shoes. And as I stated in the message... he's about 1" too high still at the bottom. So he's close to legit.