I remember having a worm bin in elementary school as well. We used to take turns collecting everyone's left over lunch to put in the bin.
I know that we had a different area of the bin for every day of the week. We'd put Mon-Fri's lunch in a different section of the bin. I'm not sure if this is important, it's just something I remember. We used shredded newspaper as bedding. We sprayed the newspaper down and then squeezed it out so it was just moist, not super wet. We also added leaves, soil, and moss from outside to make the bin a little more "homey" to the worms.
Hope that little bit of info helps. It's been a long time since I've actually been involved in taking care of a worm bin.