I never carried any more than 2 textbooks at a time in High School. We had these nifty contraptions called "lockers" that would allow you to stow your unused books on a "shelf" until you needed them. Of course, I never studied, and I did my homework in class, so...
I wouldn't begrudge someone using wheels, though. That's just smart. Assuming, of course, it's for some reason necessary to carry eight books with you at all times.
If my kid ever asks for a backpack with wheels, I'll say, "Hell no! You carry six books under each arm like a good citizen!"