A theoretical integration of research concerned with environmental variables and their effects on students’ behavior and performance is presented. The impact of classroom stimuli, such as novelty, color, noise, proximity to teacher and peers on both normal and exceptional children is reviewed. The relation between these sources of classroom stimulation and information sources (i.e., type of task and access to material, person, and role resources) is also discussed. Large deviations from optimal levels of environmental stimulation, which more often occur for exceptional than for normal children, will produce attentional and activity disruptions sufficient to interfere with classroom performance and social interaction.