The kids are divided up into groups and given specific areas to clean up. These groups are mixed boys and girls and have a couple of kids from each grade. They generally run about 6-12 kids per group. Each group has a leader, who gives a report to the 'inspector general' teacher who walks around checking and encouraging.
The kids clean up and pick up both inside and out. Yes toilets, too.
I think it is a good idea as it helps promote cooperation and tidies up the school. Win-win.
In pre school
In elementary school
In middle school
In high school