The company that arranges for the ads -- Coon Rapids' School Media's -- contacts districts about displaying student-friendly ads in the schools. A certain percentage of available space is given to ads, mostly on lockers; they also go on floors and walls. The districts get paid based on the amount of space allocated. For instance, St. Francis schools has agreed to allow 10-15 percent coverage, earning $190,000 to $200,000 a year. The ads, which are vinyl decals similar to those used on the outside of buses, are often placed across banks of lockers.