Our local school has a cardboard recycling program. There is a trailer set up for this purpose. School personnel bundle the cardboard, the recycler picks it up and sends a check to the school district.
Our group (Small Town Superheroes) thought it would be great to help! We contacted our local market to see if they would be willing to donate cardboard. They were more than happy to help! We set a pick up date a few weeks out so the market would have lots saved for us.
On pick up day, our kids filled the super wagon and truck with flattened boxes and other pieces of cardboard. The kids happily pulled the wagon to the trailer and unloaded it. During the project and beforehand we talked with our kids about recycling and the importance of it. As well as, the added bonus of the benefit to our school district!
Contact your local recycler to set up a program. Here is a link for general info on the topic: