This study investigated the relationship between the number of days spent in an elementary classroom and the reading achievement scores of pupils. Pupils attending a four-quarter, public elementary school for 200 days a year, kindergarten through sixth grade, were compared in reading with pupils attending school for 175 days per year; scores for a period of four years were analyzed. Of the 38 grade-and-year comparisons made, four comparisons were significant for the control-school pupils and two comparisons favored the experimental pupils. No consistent pattern was revealed which favored the pupils of the 200-day-calendar school. (AA)