Hello! I'm really bad when it comes to fabric names so I cam here for help. :) I'm trying to make a backpack for school and was wondering if duck canvas is a strong enough material? Thanks! ^^

This would be strong enough however it is only drycleanable so might not be your best option. I would try the heavy nylon canvas fabric they use for sports bags.
These are sturdy and you could still decorate the outside with either embroidery or a fabric of you choice,
maybe a jeans fabric (they have them in black or strips now that are really nice)

That is quite strong. It should work. I found that book corners will poke through almost anything but we had a backpack with a leather bottom that was great.