The influence of luminance level on students’ productivity, asthenopia (an eye strain), and brainfag (a mental exhaustion and depressive disorder) was studied with three typical colour temperatures of T5 fluorescent lamps. The changing rate of productivity and asthenopia were measured by using anomalistic distance determination and Анфимов alphabet test method and the changing rate of productivity was regarded as the brainfag index. It is found that medium colour temperature fluorescent lamps with appropriate exposure time can produce desirable consequences, stimulate the subjects’ cognitive ability and enhance their productivity. However, some lamps with lower or higher colour temperature produced undesirable consequences. The optimal luminances levels were thus variable and correspond to the colour temperature of lamps. The worst combination of colour temperature & luminance was identifies and should be avoided in classroom lighting design.