The reasons for teen-age sexuality are not necessarily psychological problems or cultural backgrounds. Teen-agers are people. People engage in sexual activity. Irresponsible sexual behavior might relate to the aforementioned hypotheses, but please do not confuse that with general sexual behavior.
If more adults could come to terms with the fact that normal, healthy teen-agers have sexual feelings, there might not be as many teen-age pregnancies. Parents could stress the importance of birth control instead of denying that their children are sexual.