THE rise in sexually transmitted infections (STI) among teenagers calls for a strengthening in sex education that emphasises prevention.

This is primarily a problem of adolescent health, which knowledge can mitigate. Cases were rising by 3 per cent to 5 per cent annually, to more than 800 last year, the Department of STI Control has reported.

An epidemiological perspective underscores the seriousness of the incidence. Gonorrhoea cases among most of the boys and chlamydia most common among the girls could by a quirk of circumstance well have been HIV cases, as such infections take broadly similar routes.

This is not to say the moral dimension of young people engaging in early sex should be ignored. Times and mores are changing. But prevention should take precedence over value judgments.

The next step is to construct their profile - age, social and economic background and so on - and identify similar groups for sex education sessions customised to provide them the knowledge to refrain from risky sexual behaviour.

Such a targeted approach leaves out the vast majority of teenagers, who might not need the practical tips. It overcomes the concern among some parents that teaching children how to avoid STI or pregnancy, such as by using condoms, is like encouraging them in early sex.

For those already at risk, the abstinence injunction is clearly too late. Through the Internet and an explosion in popular-culture stimuli, they are exposed to more temptations and peer pressure than their elders were. Without parental guidance, they are likely to get their messages mixed. Yet schools can only do so much.

Indeed, the Ministry of Education places on parents the main responsibility for teaching about sexual matters. The irony is that STI among teenagers are increasing despite several years of school sex education, made compulsory in 2000.

Teachers conduct it within health, science and civics and moral education. Complementing this is The Growing Years, a co-curricular package for upper primary through post-secondary levels. As part of science, lower secondary students learn about safe sex practices, such as contraception and sexually transmitted diseases. The ministry has thought out the programme comprehensively and revises it to include input from parents, teachers and students.

In reviewing its implementation and in cooperation with social organisations involved in sex education and youth issues, it could research ways to reach at-risk teenagers more effectively with useful information than it has managed so far.