For the first time in 14 years, the teen birth rate rose in 2006. After falling 34 percent from its 1991 peak, teen births increased three percent, according to a new report.

However, the US teen birth rate is the world's highest – triple that of Canada, France or Germany, and nine times higher than Italy or Japan.

A stunning 63 percent of US adolescents have experienced intercourse by the end of high school.

Every year one in 13 teen girls becomes pregnant and 4 million teens contract a sexually transmitted disease (STD). In fact adolescents account for a quarter of new HIV infections, though they are only a tenth of the population. Isn't that shocking?

This data heightens a 30-year debate over the best way to protect teens.

"Comprehensive sex education" is what most schools offer. It emphasises the use of condoms, though there is talk about abstinence as well.

"Abstinence only" is the new kid on the block, funded with $176 million of federal funds. Last April a major report by Mathematica Policy Research on four abstinence programmes stated that 2.5-5.5 years after each program, there was "no evidence that abstinence programmes implemented in upper elementary and middle schools are effective in reducing the rate of teen sexual activity."

Compared to students who did not participate, those in abstinence-only programmes began having sex at the same age and had similar numbers of sexual partners.

That report was a death-knell to abstinence-based programs in some states. Ohio, Virginia and New York declared they would no longer seek federal funds for abstinence-based programmes, since state matching was required.

Two research-based national advocates of abstinence programmes, however, strongly disagreed with Mathematica's analysis.

The Medical Institute for Sexual Health noted the study looked at only four of the 900 abstinence programmes and three of the four were aimed at black children from single-parent households: "This is an unrepresentative sample.

"Two of the programs focused on upper elementary school students, and the other two on middle school students," it added. "None of the four included a high school component."

Dr. Stan Weed of the Institute for Research and Evaluation, which has evaluated more than 100 abstinence education programmes in 30 states, asserts "the follow-up time frame employed in this study – 2.5 to 5.5 years after the programmes end – is too long for any type of sex education intervention to have a sustained effect on behavior without interim reinforcement of the programme message."

He argues that some abstinence programs work and some don't.

"The important questions are 'which ones do, and why.'"

Three years ago, this column reported the results of a programme Weed evaluated in South Carolina. Of virgins who took the course by Heritage Community Services in the seventh and eighth grades, only 4 percent began sexual activity in those years compared to 16 percent of those not in the course. Weed identified four key ingredients of effective abstinence courses:

1. A lot of programmes mention abstinence as an "ideal", but do not make a case for it. That requires at least 20 hours of teaching to affect behavior. The training must be repeated annually.

2. Well-designed programmes target teen attitudes, values, efficacy and goals regarding abstinence, sexuality and relationships. Comprehensive sex ed programmes, by contrast, think information about biology and STDs is what's needed. "However, information does not change behaviour. What matters are values –what is good and bad, right and wrong," says Weed.

3. Successful programmes utilise a variety of instructional methods that include interactive participatory activities, role-playing, skill-building personal application and commitment. Kids need to be taught how to say no to their date, and have the confidence to walk away from the relationship going in the wrong direction.

If he says, "Put out, or get out" she replies, "See ya," and walks out of the car.

4. Finally, "effective programmes pay as much attention to the messenger as to the message," says Weed.

"The teacher makes a huge difference."