 Study cohorts: a. THE BUNKEFLO STUDY: N500, aged 7, 8, 9, 12 and 15 years at baseline. In the RCT part of the study: n310 aged 7-8 at baseline. Half with physical activity and health education as intervention, half controls, all annually followed during primary school. Several other scientific institutions from the University of Lund participate as Department of Physiotherapy, Clinical Physiology, Nutritional, Paediatrics, Child Psychiatry, Teacher Training College, and Dental School, all with separate projects within the RCT. Time plan: Baseline measurements in 1999-2000, with annual follow-up measurements throughout the Swedish nine-year primary school. After that, one follow-up during the last year of secondary school 12th grade, and one follow-up at age 23-25. 