"The negative association between number of soft drink advertisement locations and participation in school lunch is a disturbing finding, suggesting these ads compete effectively with school lunches, which are designed for good nutrition," Probart notes.

McDonnell adds, "The school-supported appearance of commercial advertising in locations or in news programs may be sending silent messages that this brand might be 'OK, creating a 'halo effect. "

This study points to the need for additional research, including physical inventories of commercialization on school campuses to verify the possible impact on students. The findings may prompt consideration of tough issues because financially strapped schools may not be able to replace the revenue from commercial activity.

"However, under the 2004 legislation, schools are being asked to become zones of good health and nutrition, providing leadership in the effort to prevent childhood obesity," Probart says. "One way is for a community, parents and educators to change teens unhealthy eating habits is to develop, implement and enforce policies to create advertising-free, nutrition-friendly school environments."