The thermal and indoor daylighting behaviour of a schoolroom was investigated by using a numerical model whose reliability was experimentally examined. The schoolroom model, constructed using the modern simulation tool, has a number of south-oriented windows under which black iron plates are installed to induce thermosyphoning with arrays of upper and lower vents. A hallway is considered to cause 0.35 air changes per hour for zones by natural ventilation. For thermal analysis, simulations were carried out using the standard weather conditions and physical properties of real materials. Perfect thermal insulation was assumed for the ceiling, floor and walls between adjoining schoolrooms. Results showed that the simulation model of the present work, although simple, is accurate enough to predict the building’s thermal performance. Especially, in the early stages of designing, the results could be effectively applied to assess various aspects of design parameters in real cases without undue difficulties.