This study evaluated differences in sitting habits in the classroom between the project "Moving school" and a traditional school in 8-year-old children. Twenty-two children, since 1.5 years involved in the project were compared to 25 children in a traditional school. Making use of the Portable Ergonomic Observation (PEO) method, it was observed that children from a traditional school spend an average of 97% of the lesson time sitting statically, from which one-third with the trunk bend over 45 degrees. In the "Moving school" this posture was replaced by dynamic sitting (53%), standing (31%) and walking around (10%), while trunk flexion over 45 degrees was nearly not observed. Children from the "Moving school" also showed significantly less neck and trunk rotation. Additionally, accelerometric data showed significantly more physical activity in lessons of the "Moving school". Rates of self-reported back or neck pain did not differ significantly between both study groups. Results show that sitting habits are more favourable in a "Moving school". Further research is needed to study the impact of implementing "Moving school" concepts in traditional schools on sitting habits.