Are coeducational schools or single-sex schools preferable for secondary education? This is a theme that continues to be fervently discussed. After World War II, many Japanese secondary schools shifted from single-sex education to coeducation, which resulted in three types of secondary schools: boy’s schools, girl’s schools, and coeducational schools. Through exploring Japanese education history, the issues discussed at that time, and the ways in which coeducation was implemented, I am undertaking a study into the nature of gender equality in education.