Nowadays, people in several countries think that parents have the option to send their children to single-sex schools or co-educational schools. However, some people do not want to register their children in single-sex schools to prevent the drawbacks later in life. Personally, I agree that children should know well the opposite sex. It is because naturally there is a different character between a girl and a boy, and for that, we need to explore each other. In addition, it is to prevent sexual harassment.