Background: Austria faces increasing numbers of childhood overweight and obesity. Despite increasing numbers of studies, associations between parental body mass index (BMI) and education and the school type on overweight/obesity in students have not been reported. The objective of this study was to evaluate the influence of these parameters on the genesis of overweight/obesity in a large cohort representative of youth in Upper Austrian. Methods: A cross-sectional analysis of data from 2930 children and adolescents aged 10, 14 or 17 years from 11 different state school types was conducted. Students and their parents completed a questionnaire and heights and weights were measured. Results: Of the students 16.9% fulfilled the criteria for overweight and 5.6% for obesity, with the highest rates in the 10-year-olds (19.6% and 5.8%, respectively). While no gender differences were present in the youngest age group, the body mass index (BMI) during adolescence remained higher in boys but decreased significantly in girls. Male gender remained a risk factor through all calculations. Boys were overrepresented in schools with lower education levels and more often had BMIs ≥ 85th and ≥95th percentile. Higher parental education levels and lower parental BMIs were associated with lower BMIs of their offspring. Migration was an additional association factor for BMIs ≥ 85th percentile. Conclusion: Low parental education levels, higher parental BMIs and migration background were associated with overweight and obesity in 10-year-olds. In adolescence, male gender and higher parental BMIs remained risk factors.