I've been told by some of my colleagues that students can't donate because we are a high-need community. The kids, however, never cease to amaze me. Last year, a little guy who asked Santa for "food" for Christmas brought in a bag of Matchbox cards because he "didn't need them all and someone else could have some too". I believe that every child can learn about giving regardless of their socio-economic status. I put the emphasis on choosing a toy that they no longer play with rather than purchasing new, though all donations are praised.
Have you done a service-type project with your students?