The present study is an attempt to primarily examine thermal performance of public primary school in Assiut city, Upper Egypt (hot arid climate) targeting to identify how much time pupils achieve thermal comfort conditions in their classrooms. In order to achieve this aim the current status of a typical public primary school is investigated through field measurements in terms of thermal comfort indices. These thermal comfort indices are the Predicted Mean Vote (PMV) and Predicted Percentage of Dissatisfied people (PPD). The results show that for the recent school building design there is strong relation between indoor comfort conditions and outdoor temperature. In addition to the average measured values of both the PMV and PPD inside the classrooms were 1.17 and 38.86%; respectively. Clearly, these results indicate that a higher level of thermal discomfort is existing within the primary public school classrooms as the pupils spent more than 36.5% of their time inside the classrooms under thermal stress conditions.