We did this one last year for a lunchtime activity, and it was a blast! One student or teacher from each homeroom sat in plastic chairs, with whipped cream spread over their entire face. 5 homerooms went at one time. 3 people from the homeroom threw fruit loops at the teacher or student's face. The homeroom with the most Fruit Loops on their teacher's or student representative's face won. A lot of people came out to watch. Unfortunately you'll need at least 8 people to clean this up at a decent speed.