To evaluate the effectiveness of an engineered classroom design, 54 educationally handicapped children were placed in six classrooms, each with a teacher and an aide. Each classroom was set up with three major centers: mastery-achievement, exploratory-social, and attention-response-order. Children were assigned tasks at centers in keeping with their individual problems and were awarded check marks every fifteen minutes for behavior and work according to behavior modification principles. Achievement was tested three times over the year; daily task attention was recorded by two observers who clocked the number of seconds each child's eyes were on an assigned task during 5-minute samples taken five times daily. Children in the experimental classroom utilizing the engineered design enjoyed a five to twenty per cent task attention advantage over children in the control classrooms not using the check mark system and all aspects of the design. Experimental classes which abruptly withdrew the design at mid-year showed no decrease in task attention, in fact they improved. While reading and spelling gains were not significantly different between experimental and control conditions, gains in arithmetic fundamentals were significantly correlated with the presence of the engineered design. (Author/RJ)