First grade disadvantaged children were separated into classes by sex and taught by a teacher of the same sex. It was hypothesized that (1) single sex classes would score higher on reading and arithmetic tests and show a more positive attitude toward school, teacher, and peers than coeducational classes, and (2) the one all-girls class would score higher on reading and arithmetic than the two all-boys classes. Both experimental and control groups were given the Philadelphia Reading Test and the Philadelphia Test in Fundamentals in Arithmetic. Attitude measures were The Pupil Attitude Toward School Inventory and The Way I Feel About Myself instruments. The single sex classes scored significantly higher in reading than the control group, but there were no significant differences between the all-boys classes and the all-girls class in reading and arithmetic. All-boys classes were more positive toward school, learning, teachers, peers, and self than the other groups. The control group was more positive in these attitudes than the all-girls class. It was recommended that teacher personality and competency variables be considered in a controlled longitudinal study and that different materials and teaching techniques be stressed for training teachers to work with all male classes. (DR)