There is a new study out claiming that heterosexual teens who have sexual intercourse (meaning vaginal intercourse in this context) within romantic relationships perform academically at the same level as their abstinent counterparts.
Heather Corinna and the Scarleteen team have given the study a pretty firm critique, and the media sensationalising of the study an even bigger one. Various news reports are stating that committed relationships do less damage than casual sexual relationships or "hooking up." The study only used the terms romantic and non-romantic, which are loaded terms in and of themselves. What constitutes either to adults, let alone teenagers? The study also only suggests a correlation, not cause. There are of course, many environmental and social factors beyond sexual relationships that effect someones academic performance.