The Houston Chronicle reports on a recent study which has found that Hispanic children who learn English are far more likely to become sexually active. The author of the study claims not to know why this is so, but surely the reason is not mysterious: children who are exposed to the sewage that constitutes most American popular culture are very likely to internalize its permissive ethos and act on it. English opens the doorway to this culture, allowing hapless eleven-year olds to learn about oral sex, “threesomes,” “doggy style” and other such staples of our high-minded national conversation from Howard Stern and Friends reruns.
I have no opinion as to whether popular culture is filth, but the "Pop Culture is Filth" explanation ignores a much simpler one, which has the additional benefit of not requiring any assumption about the state of pop culture or its influence on human sexuality.
Sexual activity is affected by intention and opportunity. Pop culture may affect intention, but learning English certainly affects opportunity. If we ignore paid sex and romance novels, most sexual relationships do take place between individuals who can communicate with each other. Therefore, a Hispanic who learns English, has a much larger set of potential sexual partners, and hence the opportunity to have sex increases.
The principle at work here is similar to that discussed in Group Bias in Mate Selection and Outmarriage: the outmarriage rate of an ethnic group given a constant degree of ethnic bias will decrease as the size of the ethnic group compared to the total population increases. Here, the intention to outmarry (corresponding to the intention to have sex) is kept constant, but the opportunity to find foreigners decreases.