Here is a website for a lesson on pollution:
how people affect the environment
how pollution affects plants and animals
how to get rid of waste at school
I think this is a topic of interest that students would have a lot of thoughts and questions about
It gives students an opportunity to share what they currently understand about pollution and discuss the different experiences they have with litter and pollution in regards to the different environment they live in. The activity of collecting samples of trash around the school gives opportunity to make surprising observations of items they might not expect to find at school.