Should hair colour or the use of mobile phones be banned in schools? Permanent Secretary for Education and Manpower Fanny Law Fan Chiu-fun raised the questions in her latest letter to students, posted on the Education and Manpower Web site this week, but without giving the answers. Instead she recommended students exercise self-discipline. The web communication 'How to be a good and worthy person', marked the start of her second series of letters to youngsters. 'Students are welcome to write their views to me or discuss various issues in class with their teacher. By using real-life examples, I wish to facilitate young people in making positive, constructive and rational choices in today's Hong Kong and heighten their awareness about moral values. 'Moral education is harder to teach than other subjects,'' she said. School regulations served the purpose of cultivating a law-abiding spirit among students, she wrote. 'The degree of strictness of discipline is determined by the school's traditions, parents' expectations and the characteristics and needs of students. 'However, for students to accept and voluntarily follow the rules, they must first understand and subscribe to the rationale behind them.'' Mrs Law cited the example of Hong Kong people automatically standing on the right side of an escalator to allow people to move quickly on the left side as a manifestation of self-discipline.