Lighting systems in educational buildings should provide both for teachers and pupils an environment in which their visual needs are met so that they are able to comfortably, speedily and correctly carry out visual perception-related tasks. An adequately designed lighting system makes a school more attractive to its pupils, it increases the feeling of spaciousness and airiness, and has a positive impact on the learning atmosphere. Any educational activities that are based on visuals require quantitatively and qualitatively adequate lighting. The required level of illumination necessary for the activity is its quantitative aspect. Lighting does not only affect visual performance, it also has an effect on memory, reasoning, concentration and other mental actions. In this connection, qualitative aspects of the lighting such as illumination and luminance distribution gain in importance. The visually most challenging actions in the classroom are reading and writing as they require either short-distance perception from a written medium on the pupils’ desk or long-distance perception from the blackboard. Classrooms have to be investigated in two categories considering the content of the educational facilities; classrooms with fixed seating arrangements and free seating arrangements. The fundamental reasons to use classrooms are to present, transfer, and assimilate knowledge properly. The knowledge is presented auditory, visually or usually by using both of them. As a matter of fact, lighting in classrooms affects the visual performance; on the other hand, it has a direct relation with the performance of the intellectual activities, logical thinking and improvement in the interest.. The illumination levels required in classroom lighting vary with the kind of educational action performed in the classroom. The International Commission on Illumination - CIE defined the illumination in classrooms as 300 lx. This illumination level refers to a horizontal reference plane parallel to the floor above the bench rows and a perpendicular reference plane parallel to the writing board, walls, notice boards and maps. The standards set the horizontal reference plane 0.67 m above the floor. In order to support the interest of the pupils in their course work and to focus their attention on the teacher and the writing board, the illumination of the board must at least be equal to the horizontal illumination on the benches. Light sources should be selected with a high colour rendering index (CRI>75). In general purpose classrooms, natural and artificial lighting should be used in combination. When considering the psychological effect of lighting, the importance of daylight is beyond doubt. Daylighting in classrooms enables energy conservation and supports visual comfort, however, daylight apertures cause glare and solar heat gain during the overheated period; to secure optimal conditions both negative effects need to be controlled. The primary school buildings in Turkey are lacking of comfort conditions due both to economic reasons and to deficiencies during project design and implementation. This study presents the main findings of the research project entitled “Investigation and evaluation of primary schools in terms of visual comfort conditions”, which was carried out by the Istanbul Technical University Faculty of Architecture. 18 classrooms in 8 primary schools in Istanbul were investigated in terms of the visual comfort conditions during the academic years 2006-2007 and 2007-2008. The study was carried out in the following steps; determination of the exterior conditions of the building, determination of the building form and orientation, determination of the specifications related to the classrooms, daylight apertures and the artificial lighting systems. Basing on the collected data, evaluations on the level of sufficient illumination, control of direct sunlight, combination of natural and artificial lighting and the general maintenance of the artificial lighting system. As a result of the present work the need for a more precise approach towards the lighting in primary school buildings both in the design phase and during their actual usage is emphasized. Such an approach would ensure that visual comfort conditions are achieved and energy consumption is reduced with a positive effect on the country’s economy. Its implementation would at the same time raise the level of awareness for a sustainable environment.