For once the dutiful disclaimer understates the case. "The following program contains language and sequences some viewers may find disturbing," says a preface to "Children of Darkness," a documentary on public TV tonight. In fact, the whole program--a "Non-Fiction Television" presentation at 9 on Channel 32 and at 10 on Channel 26--is disturbing, even offensive, and not for the reasons the filmmakers intended.

The producers start out very shabbily, at Word One. Even before the disclaimer, the documentary attempts to grab viewers with a "tease" that includes scenes of afflicted children going through garish agonies while the rapt camera watches. An announcer strokingly intones that there are "over 7 million mentally ill and emotionally disturbed children" in this country, but that isn't precisely what the program is about.

What the program is unconsciously about is how not to make a documentary. This one, produced and written by Richard Kotuk and Ara Chekmayan, starts out with a portrait of an engaging young man named Brian, a schizophrenic patient at Eastern State mental hospital in Pennsylvania. On Sundays, Brian's 70-year-old father, though he lost a leg in an auto accident, picks Brian up and takes him home, where Brian keeps company with a priceless, devoted girl named Linda who thinks the world of him.

The film seems approving of Brian's life outside the hospital and critical of his life in it. Throughout the hour, it is implied that the use of psychotropic drugs to control potentially violent and self-abusive children is somehow improper and inhumane. It's humane, I suppose, to zoom in on the face of a screaming hysterical child having a fit or weeping in agony? Filming patients within mental hospitals is an extreme, arguably ultimate, invasion of privacy. Frederick Wiseman justified this intrusion with his classic "Titicut Follies" in the '60s; a greater good was being served, because the film exposed deplorable conditions at a Massachusetts mental hospital. (The state responded swiftly--it banned the film.)

But those who made "Children of Darkness" do not evidence the compassion or the filmmaking skill to justify intrusion. The film at times seems a horrible field trip for voyeurs. It is more cruel than the treatments it so vaguely deplores.

The case of Brian, which could have made a documentary in itself, is summarily dropped so the film can move on to its two amateurish attempts at "60 Minutes"-style investigation. The Elan residential treatment center in Poland Springs, Maine, is visited, and found to be a miniature totalitarian state that specializes in humiliating and even brutalizing young people kept there. The problem is, these are not emotionally or mentally ill children, but sociopaths who have had repeated problems with the law or with drugs. So this section of the documentary really has nothing to do with the rest of it.

Finally, there are shocking allegations about the South Beach Psychiatric Center in New York, where three young people died in mysterious circumstances soon after being admitted to the center in recent years, and where other patient deaths go unexplained. As journalism, this section of the documentary is incomplete and inadequately documented. Instead of hard reportage, the filmmakers give several minutes to the demonstrative grievings of one victim's parents. At a certain point, their desperate testimony seemingly stops being naked emotion and starts catering to the camera's demand for drama.

"Children of Darkness," such a sorry excuse for a documentary, even includes a sorry excuse for sorrow.