I agree with the posts that suggest taking any bag for the checked bag. If he's going to check the bag and not use it for his weekend trips, I think a bag with wheels might be useful for transport to and from the airport; I've heard, however, that wheeled bags are not great if you're using them extensively on cobblestone streets, which you're more likely to find in Europe than here.
I realize a lot of students like to carry a laptop in a small backpack, but since he still should have the option of both a carryon and a personal item, I've found this combination extremely useful for traveling:
The REI Stuff Daypack is one of those compressible packs that folds into a pocket to the size of a small hat. When unpacked, it's capable of carrying a pair of shoes up to about a size 10, enough clothes for a weekend, and a small baggie with toiletries--
http://www.rei.com/product/809163/rei-stuff-travel-pack. I've stowed this bag in the smallest of overhead bins on regional jets with no issues whatsoever. Since the fabric is flexible and fairly thin, it's lightweight; for those very reasons, however, it will not be suitable for packing a laptop unless the laptop itself is in its own protective sleeve. If he doesn't need to carry anything in it on the plane, it'll pack easily into the checked bag. And he might not want to pack anything in it on the way over there so that he'll have extra room to pack mementos, souvenirs, etc. for the trip home.
I'd put the laptop in the personal item he can place under his airline seat. There are plenty of such bags that meet most definitions of a "personal item" (generally limited to 36 linear inches), but I've found this one useful:
http://www.ebags.com/product/calpak/...roductid=59743. There's room for a laptop, pens, pads, etc. with a little room left over to pack a few other things (I bought this bag specifically because its dimensions allow me to put a 15-inch packing folder into one of its main pockets). I generally pack my laptop in a small sleeve that I can then carry separately when I'm on the ground and don't want to haul a briefcase-sized bag. The sleeve also offers a little extra protection for the laptop when packed.
Of course, if he's insistent on a backpack, these recommendations will miss the mark, but if he's flexible, I think he could find this combination pretty useful.