This paper reports a research project developed in partnership with the Principal and Leadership Team of an Australian secondary school. It monitored a school-based initiative designed to address the underachievement of male students. Students in Year 9 selected single-gender or coeducational classes in mathematics and English during the second half of a school year. Student scores in standardized tests and school-based assessment in these subjects were obtained before and after the establishment of the initiative. Results indicate no significant difference in mathematics achievement that can be attributed to gender or class composition. However, scores in school-based English improved for students in single-gender classes. Improvement for girls in single-gender classes was greater than that for boys in single-gender classes.