Background:The increased infantile obesity rates are related to faulty dietary intake (DI) and physical activity (PA) habits, that are probably related to a prolonged stay at school during the day. Aim: To investigate DI and PA among elementary and high school students and their association with type of school that they attend. Material and Methods: Quality of DI and PA was assessed, using specially designed questionnaires, in 1136 elementary school and 1854 high school children attending public schools managed by city halls (ME), subsidized private (SE) and private (PE) of the Metropolitan Region. The responses to the questionnaires, were qualified using a numeric scale that ranged from 0 to 10 points. A higher score indicated a better habit. Results: Percentile 25 (p 25 th) PA score was 4 and 3 in elementary and high school children respectively and the p 25 th for DI were 5.7 and 4.3, respectively. No differences in DI scores, according to the type of school, were observed. However, physical activity scores were significantly lower in children and adolescents from ME schools than from PE schools. Sixty percent of ME schools had less than 2 hours per week of programmed physical activity compared to more than 3 hours, in 70% of PE schools. Elementary school children and high school adolescents expended 8 and 11 hours per day, respectively, in minimum expenditure activities. Conclusions: There is a greater deterioration of PA than DI among school age children and adolescents. Those attending ME schools have the worst physical activity scores. This fact must be addressed in future healthy lifestyle encouragement policies (Rev Méd Chile 2008; 136: 53-63). (