Exploring why more boys than girls continue to study higher levels of mathematics in senior school when there appear to be no gender differences in achievement in earlier years is worthy of investigation. There are potentially many reasons why this occurs including career aspirations, interest, and attitudes. One factor explored in this study was the gender composition of classes in Years 7 to 9. Data were collected from students in a single-sex boy's school, a single-sex girl's school and a coeducational school. Data revealed differences in attitude to mathematics with girls in the single-sex school having the most positive attitudes and girls in the coeducation setting having the least positive attitudes.