Students in a single sex school are equally competitive. In a study in The University of Chicago Graduate School of Business, they had 140 students (75 boys and 65 girls) run a race. When the children ran alone, there was no difference in performance. In competition, boys but not girls improved. The girls in the study did not perform worse, but simply the same, as if there was no competition at all. On the other hand, the boys put much more effort into their performance once they were competing.