On Friday, I'm mentoring a student at a local high school who has a passion for writing, and a strong interest in writing for games.  What advice would you suggest for him?  What advice would you suggest for me as an advisor?  (Me personally, I've been designing/developing games/apps for a while, but I haven't personally put much thought to writing for games)

 - Thanks!

Your young friend should get the best grades he can, then go to college and get a degree in writing. While he's doing that, he should become familiar with online forums and ask for additional advice himself along the way.  You should start a second thread with your question for advice for yourself - in the forum most suited to what you want to do.

I work as a game designer and scriptwriter for an indie studio, and If I had to give some advice for young writers, I'd tell them to do some writing/grammar main courses, because writing a video game story is not the same as writing a novel, for example. Structure is quite different. Novel works in chapters, but video game depends on the game genre. 

Before start writing the story game, he should think about all the lore behind (I mean, all the backdrop of the game). I'm talking about the whole universe where the characters will move, and so the skills, abilities, attributes, an appropiate timeline and how divide it in slices/levels.

Once you know and understand the whole universe you just created, you can do the structure. Structure depends on the genre. It is not the same structure for a 2D platform video game than a Racing Video Game, for example. But, as a lore fanatic, I'm always looking for the story behind each every game.