I would recommend either LL Bean or Wenger/Swiss Army
I had at least a dozen friends in college that were still using their LL Bean Backpacks from Junior High! 4 years of Jr. High - 4 years of High School - and 4 years of College.
12 years out of a backpack is astounding!
As long as they avoid stressing the zippers, and don't drag them - you will get your $$$$ worth out of an LL Bean Backpack.
I had a Wenger backpack that was stolen in college - it was the absolute best backpack I have owned personally.
The backpack I use now was one of two purchased at the same time in 1996. I had a green one, and my brother had a blue one. The zipper broke on mine (the green one) and since my brother was no longer using his, I inherited it. They were made by Spalding back before Spalding started selling inferior products.
We own several LL Bean tote bags and their products are built to last.
As a general rule - well made backpacks DO NOT come from Wal-Mart!
Look to see if there is an LL Bean factory outlet near you!