What Jan Sport backpack can hold the most?

I carry a lot of books for school and I need a backpack that can hold it all. I am fashionable and a girl. I am a big fan on Jan Sport bags, but should I use a different brand. I need a backpack that goes on my back because there are lots of stair at my school. I was looking at the Merit, All Nighter, and the Big Student. I need help!!! Thank you!!!