Here are some other websites that you will find useful:

Lesson Plans

Temanaotemoana

British Council

Kids against Plastic

Bag It

World Environment Day Afval op School

Environment California

The Story of Stuff

Surf Rider

Less Plastic

Ocean Heroes 

Taking Action

Greenpeace

Sea Shepherd

The Ocean Cleanup

Captain Planet Foundation

Posters and Artwork

B Alternative

Thant Myanmar

More information about Zero Waste

Circuit Zero Dechet

Courses

MOOC on Marine Litter: UNEP Open University of the Netherlands 

Zero Waste France

Nat Geo Learning: Collecting Data to Explore Plastic Pollution in Our Communities