Adopt-a-Quad

The Adopt-a-Highway program has become a popular program in many states. Here's how you use it.  Ask the principal if your group can be responsible for keeping a high traffic area of the school trash-free.  All you'd like is to be able to post a sign saying something like "youth alive keeps this area clean."  Assign a person for each day of the week to spend 3 minutes picking up trash in that area.
If you have a lot of people, you could graduate to the football stadium.  Let the activities director know that your group will clean the grandstands if the announcer will announce just that.