This research finds that teacher effort in reading instruction is associated with student achievement in the primary and middle grades. Teachers who exert a greater amount of effort on the job in reading produce higher reading achievement scores in their classes at both the primary and middle-school level as measured by the Stanford Achievement Test. The negative effects of low effort were more pronounced in the middle grades than at the primary level. Five reading consultants in a suburban New England town rated their teachers on the Teacher Effort Scale in Reading, a scale designed to differentiate between those teachers who manifested a great deal of effort in their work and those who did not. Efforts to secure and utilize supplementary materials, provide differentiated instruction, keep records of student progress, and arrange conferences dealing with each individual student's progress were scored on four subscales. The mean reading scores of 37 classes of high-effort and low-effort teachers were then analyzed by using a two-way analysis of covariance technique. (Author/MKM)