If the school bans certain containers and the children must take them back home, this is an opportunity to explain why some items are threats to the environment. Children are often willing to speak to people who are littering, but they are afraid of the reaction they may get. Talk to them about this. Explain that even though people may appear not to listen at the time, or may even be angry, they may think about it later and indeed may change their behaviour. Have the children do some role play or a small skit, so they can devise mechanisms for coping with an angry reaction from adults or their peers.
Schools often have a variety of activities on their grounds.
A fair or fun day may result in large amounts of garbage and a return to a dirty schoolyard. Have a team of children with a supervising teacher present to ask people to use litter bins and even pick up garbage themselves. Schools are often associated with churches. Encourage the children to talk about managing garbage at church meetings. PTAs, Girl or Boy Scouts, or cadets should also be involved in the garbage programme.