1 Department of Sociology and Anthropology, Concordia University, Montreal, Québec, Canada. skairouz@alcor.concordia.ca

Objective: To evaluate the impact of a smoke-free class competition in elementary schools in Québec, Canada before widespread dissemination of the program across the province.

Methods: In a quasiexperimental study design, 843 students in 27 schools exposed to "Mission TNT.06" were compared to 1213 students in 57 matched comparison schools. Baseline data were collected in grade 6 prior to implementation of the program. Follow-up data were collected in grade 7 after students had transitioned to secondary school.

Results: The program improved knowledge about the harmful effects of second-hand smoke, but had no impact on knowledge about the harmful effects of smoking, attitudes about the acceptability of cigarettes, beliefs about the tobacco industry, or self-efficacy to resist peer pressure to smoke. After exposure to the program, intervention students were more likely to misreport their smoking status and to report unfavourable attitudes about classmates who smoke.

Conclusion: Mission TNT.06 may encourage young smokers to misreport their smoking status and to marginalise classmates who smoke. These findings prompted recommendations to conduct more in-depth evaluation of the smoke-free class competition before widespread dissemination of the program across the province.