During the last decade different types of sustainable schools were built, from highly insulated schools to Passive House schools. However, there is danger that the focus on energy reduction leads to less attention towards the quality of the indoor environment and the thermal comfort. During one week the most important parameters related to Indoor Air Quality were measured in three highly sustainable and one more standard recently completed schools. To be able to draw conclusions about the Indoor Air Quality the results of these new schools were compared with those of earlier measured school buildings. The evaluation of four measured recently finished schools enabled us to find out the effects of the design concepts which were more focussed on sustainability than normal for schools. Dutch schools have to meet the Dutch Building Code, which recommends a level of 1000 ppm CO₂-concentration with a maximum of 1200 ppm. The latest more strict Dutch design guide ISSO 89 should lead the path to better IAQ in schools in the Netherlands, with the best being class A. Clearly from the measurements it shows that neither of the new schools reaches quality level A, level B is the best result and some school perform even conform class D which is unacceptable to the latest Dutch guidelines. Therefore a new design approach is necessary with more focus on the Indoor Air Quality for school building.