In this research the thermal comfort and thermal comfort parameters for children in primary school classrooms has been investigated. Actual thermal sensation and clothing insulation of children (age 9-11) in non-air-conditioned classrooms in three different schools in the Netherlands have been obtained. Results are available for a total of 24 days, covering winter, spring and summer conditions (year 2010). Questionnaires have been applied to obtain the actual thermal sensation and clothing insulation in the morning and afternoon of regular school days. In this period physical parameters (temperature, relative humidity, etc.) were recorded as well in order to derive the PMV. The results show that children adapt clothing during the year from mean values around 0.9 clo in winter to 0.3 clo in summer, with the largest changes occurring in the mid-season. There is a small difference in clothing adaptation between male and female children, with the females showing more adaptation. Comparison of the actual mean vote with the calculated PMV, based on the measured data, indicates a clear difference. The conclusion is that the PMV model does not predict the thermal sensation of these children accurately; it underestimates the mean thermal sensation up to 1.5 scale point. When the actual thermal sensation votes are compared to comfort predictions based on adaptive temperature limits it shows that children prefer lower temperatures than predicted by these methods.