Many people claim that single-sex (SS) education is better for students than co-educational (CE) e.g. Jackson (2016). There have been criticisms of this idea e.g. Halpern et a. (2011) but generally it is believed to be beneficial. But what does the evidence suggest? A large-scale meta-analysis by Pahlke et al. (2014), involving 184 studies and 1,663,662 students, compared them on a variety of variables (mathematics performance; mathematics attitudes; science performance; science attitudes; attitudes about school; gender stereotyping; self-concept; interpersonal relations; aggression; victimisation; and body-image) to see if attending a SS school benefited males, females, or both.