I know there are better packs out there but for around town, school, etc, are they pretty decent?
You get what you pay for in most cases. A cheap pack is a cheap pack is a cheap pack.
Volume and density (or weight per volume) are important considerations. Almost any pack will carry an extra sweater, loaf of bread, etc. When you carry books, glass bottles (water in Europe, pickles, peppers, etc.), canned goods, the quality of the material used, stitching (and thread type), and zippers (size and brand - YKK large teeth :thumbup

become much more important. As total weight goes up you need to pay more attention to the shoulder straps and hip belt (suspension) so you don't put all the weight on your back. "Barrel backpacks" (sack with the zipper at the top) seem to be a little more durable as well and won't dump your stuff IF the zipper fails. A good central carry handle or hook loop is important too when you are lifting it to or from an overhead train or airplain storage rack.
At 58% of my body weight, my knees start to give out with descending long staircases and steep hills being the worst (yes it's easier on the knees to go uphill

). I like internal frame packs. Lowe Alpine used to be my favorite brand. They seem to have gone down in quality for a more mainstream price-point today. Osprey and Gregory get my attention today but, my older Lowe Alpine packs are still serving me well (one is almost 20 years old and I lived out of it for 6 months in one stretch).
For a smaller lighter duty pack, I picked up a Deuter (German brand) that while made from lightweight materials has a good suspension system in it, has really good padded shoulder straps and a hip belt, a built in rain fly, and the aluminum frame keeps it off my back so I get some air cooling and I don't have a sweat soaked shirt when I get to my destination. The pack works out really well until I start putting canned goods or glass bottles in it. The weight and hard edges dig into my body a little too much.