Prairie Farms Dairy Inc., the Milk Processor Education Program (MilkPEP), and the St. Louis Dairy Council are trying different flavors and packaging to try to increase consumption. About 300,000 students in 421 schools are participating in the test.

Not every school is receiving the same set of flavors. Some receive more than others, and some schools have different packaging. One district's schools, for example, are receiving cartons with pictures of children playing sports on them.

Rita Duncan, executive director St. Louis District Dairy Council, said the study grew from the work done by the National Dairy Council in 2002 on both coasts and in Florida that found milk consumption increased by 18 % when schools offered the milk in plastic bottles. The study also showed that children who drank bottled milk finished more of it.

But Duncan said the bottles were twice as expensive as the plastic carton. "We are looking at whether we can make a more affordable package-an attractive paper carton-and still have the same result," she said.