I'll give you some advice....BUT at 6'6" , as long as he is a decent athlete, a D 1 school will gobble him up. They are more interested in POTENTIAL....like frame size (how much room does he have to grow), athleticism (his vertical jump, 40 time, reactions, quickness). A scout is more likely to ask a kid if he can dunk a basketball before he asks what a kid can bench, the bench can be improved, if you'rr a lug who can't walk and chew gum at the same time, there isn't much any weight program can do for you. Most big schools aren't overly concerned about a kid who is underweight and a little weak so long as potential is there, he'll redshirt his first year, but a place like Nebraska will get him on a steady diet of squats and pulls, and as a scholarship athlete, he'll have unlimited access to force feedings at the training table.
That said, to save him the frustration of getting thrown around out of the gate, he needs to EAT....get in his protein and then anything else is fair game. So long as he gets good at squats, deadlifts, bench presses, overhead presses, he'll be fine.......5x5 training would be perfect.
Honestly, if a D 1 or 1-AA school doesn't swallow up a 6' 6" kid, his problem isn't strength-related. If he has a small frame or if his vert is 20", that is gonna damn him, lol....but if he has room to fill out and he is at the least a better than average athlete, he'll be fine, lifting and eating is hard work, but doesn't require any God-given abilities.