Background The promotion of healthy eating and physical activity within school settings is an important component of population-based strategies to prevent obesity; however, adolescents may be vulnerable to weight-related messages, as rapid development during this life stage often leads to preoccupation with body size and shape. Objective This study examines secular trends in secondary school curricula topics relevant to the prevention of unhealthy weight-control behaviors; describes crosssectional associations between weight-related curricula content and students' use of weight-control behaviors; and assesses whether implementation of school-based obesity-prevention policies/practices is longitudinally related to students' weight control behaviors. Design The Minnesota School Health Profiles and Minnesota Student Survey (grades 9 and 12) data were used along with National Center for Education Statistics data to examine secular trends, cross-sectional associations (n=141 schools), and longitudinal associations (n=42 schools). Main outcome measures Students self-reported their height and weight along with past-year use of healthy (eg, exercise), unhealthy (eg, fasting), and extreme (eg, use laxatives) weight-control behaviors. Statistical analyses performed Descriptive statistics, generalized estimating equations, and generalized linear regression models accounting for school-level demographics. Results There was no observable pattern during the years 2008 to 2014 in the mean number of curricula topics addressing unhealthy weight-control behaviors, despite an increase in the prevalence of curricula addressing acceptance of body size differences. Including three vs fewer weight-control topics and specifically including the topic of eating disorders in the curricula was related to a lower school level percent of students using any extreme weight-control behaviors. In contrast, an overall measure of implementing school-based obesity-prevention policies/practices (eg, prohibited advertising) was unrelated to use of unhealthy or extreme behaviors. Conclusions Results suggest obesity-prevention policies/practices do not have unintended consequences for student weight-control behaviors and support the importance of school-based health education as part of efforts to prevent unhealthy behaviors.