Having done (and currently doing!) the college thing, the S25 is a great bag, UNLESS he's going to be carrying more than 1 or 2 textbooks and a binder. The shape of it isn't all that great for more binders or books. I'd suggest the Brain Bag (though I don't have one) if he wants to be able to bring more than that with him, though it'll be HEAVY.
I've taken electronic notes of some sort for 15 years, so I don't tend to have many binders (unless the class requires a lab notebook or something), and I'll load up the *completely legal copy that I totally purchased legally* ebook of my textbooks, so that lightens the load quite a bit, too. The only time I had a problem with the size of the S25 is when I had 2 classes from 9a-6p, Friday and Saturday, both of which required a lab notebook and workbook... That was a tough couple days a week.
TL;DR: If he's going to have most of his stuff digitally, the S25 is great. If he's going to insist on bringing all his books and notebooks everyday, consider the BB.