I live in a neighborhood that the families of students could not contribute much in the way of money or school supplies. Some school districts are top heavy, but still teachers need to spend their own money to decorate their classrooms or do special projects.
A nearby college had a supply drive, placed a huge box near the library door, collected back packs, paper, pens, folders, etc., and donated them to local schools.
Advertise in the PennySaver in the items wanted section. List specific items such as colored pencils, construction paper, group craft projects, etc. Have volunteers pick up the supplies or have a drop off location.
My mom, a teacher, would contact a manager of a 5 & dime, drug store, or fabric store. Say she had little to no money and ask if they would fill up the bag she brought in with any scraps they were going to toss out. She'd get paper, stickers, ribbons, and card stock. Sometimes they would give her two bags. She'd take what she could use, then pass it on to another teacher.
At a local fast food restaurant (like McDonalds or Burger King) have a supply drive. See if the restaurant will offer free fries with an order of a sandwich and drink with any supply donation. Have it last from 2 PM to 4 PM, so it doesn't affect the lunch or dinner crowd.
In the PennySaver or other classified ad paper, or from parents ask for donated items that can be raffled off. Or do a money raffle. Have the raffle during a PTA meeting.