Background: This study assesses socio-economic health inequalities (SEHI) over primary school-age (4- to 12-years old) across 13 outcomes (i.e. body-mass index [BMI], handgrip strength, cardiovascular fitness, current physical conditions, moderate to vigorous physical activity, sleep duration, daily fruit and vegetable consumption, daily breakfast, exposure to smoking, mental strengths and difficulties, self-efficacy, school absenteeism and learning disabilities), covering four health domains (i.e. physical health, health behaviour, mental health and academic health).Methods: Multilevel mixed effect (linear and logistic) regression analyses were applied to cross-sectional data of a Dutch quasi-experimental study that included 1403 pupils fr...