That's an easy one
Have a Presentation at all schools that says what's needed at school for participation, you can offer movie tickets ,skating, bowling etc if a student could write a small essay about recycle and it's future. Have the movie theaters do a trailer on the most importance of recycling.

Also have them bring paper or plastic to the picked event where there is a recycle bin located, as part of the requirement to get admission. Kids love that stuff.