Issue students with gloves and dust masks and have them record the number and type of garbage in the drums at the end of a school day. Ensure they wash their hands afterwards. Each class can be responsible for counting garbage for one term, so that everyone gets a chance. This is relatively easy to do in a small school with young children. They regard this as a game and enter into the activity with enthusiasm.
Older children are more difficult to motivate.
If your school is a secondary school with a large student body, use the youngest children and the members of any environmental club to do the Garbage Audit. Make a graph and post the results around the school. Explain to the children that the goal is to reduce and manage garbage better and a Garbage Audit is the first step. The second step in managing garbage is to teach children that not all garbage should be thrown away. Waste should be separated and used for different things.