These days, I'm working on installing a rear rack on my bike and thinking about carrying options for various situations. Yes, I plan to get at least one pannier in the near future. However, I almost certainly will continue using a backpack for school while biking to and from there. So in order to avoid the disadvantages of riding with a backpack on my back, how should I carry a backpack on the rear rack?

Here are some options I considered:
1. Secure backpack to the rack using bungee cords or a bungee net
2. Attach a collapsible (or not, I guess) basket/crate on the rear rack and simply drop the backpack inside

You're welcome to chime in with alternatives to the above two options, but please remember that in this situation, using a backpack but carrying it on my bike and not on my back is the given condition to work with.