"Teen Sexuality" opens with a pelvic montage and doesn't get much more subtle as it goes on. The locally produced informational hour, at 10 tonight on Channel 4, is aimed at puberty-stricken teen-agers and their parents and was produced in cooperation with Planned Parenthood.

The goals may be commendable but the execution is execrable, a gosh-and-golly approach to the topic that, in tossing together interviews with sex educators, comments from kids and crudely dramatized improvisational vignettes, twirls itself into disarray. It is something of a reverse accomplishment for a network-owned station in a major market to have produced a documentary that looks this crummy.

On the other hand, it wasn't produced for looks, and there may be many in the audience who will benefit from the counsel being offered. Subjects like birth control, sex education, Saying No, and pregnancy are covered. Viewers are given an address to write to for additional information prior to each commercial break. The kids themselves seem encouragingly bright; "love is being better-than-a-friend," one boy says. Another notes that to impress girls today a guy has to have money, drive a car and "dress GQ." A younger lad says sex education includes discussions of "sexual organisms on the body."

It would have made more sense for the program to deal with the topic of sex education as it is practiced, or malpracticed, in Washington-area schools. Instead it gets into sex educating itself; menstruation and ejaculation are illustrated with animated diagrams. The propriety of this is questionable, despite an elaborate advisory at the top of the hour.

Lea Thompson and Henry Tenenbaum seem to be the correspondents, but they pop up only now and then. The program in effect is narrated by the editing, which leaves it, by and large, self-defeatingly incoherent.