I'd just like to add, to the post above, that Teens are hungry for reliable information. But they are often too shy to ask, or don't know what to ask. Acknowledge that they are sexual, that it's difficult to talk about and also that sex is going to be a big part of who they are for quite a while and that a sub-set of Teens will also be involved in intravenous drug use. As well, other recreational drug use, including alcohol, can and often does, lead to poor sexual decisions being made while under the influence of alcohol or other drugs.
Best of luck to you!