"Sex and the American Teenager" may be a sure-fire TV title, but it isn't a grand example of truth in packaging. The teen-agers interviewed for this undistinguished Home Box Office documentary are all from the Philadelphia area, so "Sex and the Young Philadelphian" would be a more accurate label.

It's hardly worth debating, though, since the program, the latest in the "America Uncovered" series, and premiering tonight, is only marginally worth watching.

Not that some of what the interviewed adolescents have to say isn't intriguing. Sexual intercourse, says one boy, is "a great way to express our feelings to each other." But the interviews are supposed to illustrate and annotate the results of a national survey, and often they don't. The statistics rattled off by an announcer are not necessarily followed up with exmaples relevant to them.

One young woman says very casually that she has had a sexual experience with another woman and that her mom just didn't understand when told about it. This relates to nothing quoted in the survey. Indeed, the logical suspicioon is that this tidbit was inserted for its titillation value.

One does get a certain insight into the exploitational ethics of the instant-gratification generation. A teen-age father whose girlfriend became pregnant at 14 says he wants to go from a menial low-paying job into professional boxing "so I can get mine the fast way." A 16-year-old named Joe says that when he is dealing with women, "My strategy is, mostly like, let 'em think that you love 'em . . . then you can get anywhere you want most of the time."

Joe's combative view of the male-female relationship is not really new. He says that "falling in love is the worst thing that can happen to a guy" because the women can "tie you around their finger." After this misogynistic utterance, Joe begins to weep when he talks about society's standard for masculine behavior. This is moving up to a point, but the interview is a little too neat, almost as if it had ben scripted or coached.

HBO does not produce documentaries; if only finances or buys them. There is no HBO News, as there is a news division at most commercial networks. So there are no HBO standards and guidelines about what can be passed off as real in a documentary. There are aspects to "Sex and the American Teenager" that seem manipulated or finessed, interview revelations too pat to be true.

The best television essay on this subject has never been seen on television: "Seventeen," the sixth and concluding portion of the landmark Peter Davis documentary, "Middletown." PBS declined to show it in 1982 out of fear of litigation and only now is it appearing sporadically in theaters. Its fiery controversiality was a sign of its integrity. By contrast, "Sex and the American Teenager" isn't likely to engender any more heated disclosure than the average episode of "Family Ties."