Here's a great program from UCONN Connecticut Sea Grant. It's a good connection to the fourth grade unit on watersheds and the Long Island Sound. It's a super fun, hands-on way to think like scientists about pollution and natural systems.
http://seagrant.uconn.edu/publications/marineed/LISINJAR.pdf
The Conservation Commission has all the tools needed. Green Schools is working on a way to make this program available as a kit to bring into the school.