A) The school health program
Within the School Screening Program, 15‐20 school nurses screen all students of C2, P4, S1 and S4 of all schools (~5500 children) every year since 1998. The mean age of students at these grades is 5.4, 9.2, 12.5 and 15.5 years, respectively. Students are also asked about tobacco use, alcohol use, substance use, and physical activity. Anthropometric variables and blood pressure are measured in all students. The use of same methods to assess overweight and obesity allows comparing findings over years. Overweight and obesity in children are defined along the standard age and sex specific criteria of the International Obesity Task Force (IOTF).
B) Overweight and obesity
Participation to the school screening program in 2015 was 79% (4278 from 5439 eligible students in C2, P4, S1 and S4), which is fairly satisfactory. Some non participation is expected and can relate to different factors. First, some obese children decline participation; this non random factor may lead to underestimation of the true prevalence of obesity. Second, school nurses often lack time to complete the screening program due to competing duties at health centre level; this random factor does not alter the validity of the prevalence estimates. Good organization by the school nurses and maintaining adequate equipment and facilities for screening are also important factors for the smooth functioning of the screening program.