Chewing gum in school is not just OK around here. It's required.

Some 4,000 elementary school students in Polk County will take part in a two-year study on sugarless gum and cavities."We're certainly not going to have to fight to get kids to do this," said Stephen White, principal of Hillcrest Elementary School in Lake Wales, one of 13 Polk County schools participating in the University of Florida study.

The schools' teachers, who have been telling students for years to "spit out that gum," agreed to the study after a presentation Tuesday by Anthony J. Conti, a professor of dentistry.

Research has shown that sugarless gum prevents tooth decay in children by reducing plaque, Conti said. The study will compare two sugar substitutes used in gum, sorbitol and xylitol.

Starting next week, the students will be required to chew gum for 10 minutes each day at school, as well as at home. Participants will receive toothbrushes and free dental checkups.