Sex is pretty wonderful for your health and metal well-being, if you minimize the threat of STIs and pregnancy.
Education and programs that allow the under-aged access to healthcare facilities that specialize in sexual health and family planning seems to be the more healthy (and more sustainable and achievable) alternative to abstinence advocacy.
I think that anyone that believes that teenage abstinence is at all achievable is probably delusional, or at the very least heavily sheltered, on the topic.