Pass the hat and ask diners to contribute. Explain where the money will go. Teachers have made videos of their classroom over the course of the year and auctioned them off to parents. Restaurant and theater owners can donate dinners and seats to shows. This takes some organizing but can raise lots of money for your cause and will alert the community and get everyone involved as well.
Students can create posters, canvas the neighborhood for donations, etc.
FAST - Give up one meal a week or give up junk food for one week and donate the money to a cause. Get the school involved by going around to other classes and explaining where their money will go. Place large containers in each classroom in which students can place their change. For instance, in autumn ask participants to bring a seasonal dish. Eat outside under colorful trees.