I think coeducation is much better as you tend to become more familiar with the opposite sex and have friends from both sexes so that depending upon your problem you can call on boys or gals for help.
It promotes healthy interaction between boys and girls..

Girls & boys at a self conscious age take extra care of themselves. Growing up together and sharing activities such as dramatics, art and other things like socials, widen the students talents and a healthy atmosphere pervades in all co-educational schools. The spirit of co-operation that grows between boys and girls makes it easier later on to adjust in a mixed society. Boys become aware of girls' abilities and vice versa. A spirit of co-operation and competition thrives in the co-educational system.