They shouldn't overlook food, along with whatever training plan. Do they know how to/are they allowed to cook for themselves? I'm a fan of having kids learn to boil eggs and cook stuff in a pan if they can.
Wendler did outline his approach to training kids with 5/3/1 here. Dan John (who has a ton of experience with high school athletes) has his Southwood Program that's also a solid option. There's really no "wrong" choice since all the programs teach the fundamentals, and any consistent well-designed program they do will be beneficial.
I do also always recommend younger lifters be able to run through this bodyweight plan before getting to weights.
If your kids are still in the off-season for everything, then any of the plans will be fine. If they're in-season for a sport, 5/3/1 is more adaptable but Starting Strength would be more difficult to follow properly when doing a lot of practice/games.