The underachievement of boys in school seems to be the general norm in many countries. Many studies have tried to find the key to this problem; still, no one seems to have found it. Studies about brain research, boys’ attitudes or motivation are trying to find the final solution and the appropriate strategies to address the problem. This degree project has chosen to explore if single-sex classrooms can enhance boys’ achievement in the language classrooms. Many scholars seem to be convinced that single-sex teaching can be the solution of the underachievement of the male students in compulsory schools. However the findings of this degree project show that more work must be done in this field to accept single-sex teaching as the solution to close the gender gap. Many recent articles, books and documents about the actual topic have been reviewed to give some light to this degree project.