If you feel like you've already read quite a bit about the documentary "Bully," you have. But that still won't prepare you for the experience of seeing it.

"Bully" has been in the news a lot lately because it received a restrictive R rating (for a small amount of bad language) and then chose to go into theaters unrated. Its distributor, Weinstein Co., made that choice because the film's subject matter, the pervasiveness of school-related bullying and what can be done about it, would seem to cry out for a high school age and younger audience. And "Bully" has an emotional impact that must be viewed to be understood.

A passion project for filmmaker Lee Hirsch, who also served as his own cinematographer, "Bully" hopscotches around the country looking at the situations of five different children who have suffered the effects of bullying.

Two of these children, however, are unable to appear on camera. They're represented by their parents because they were driven to suicide by persistent taunting, a situation that is every bit as disturbing as it sounds.

For as difficult as it is to watch children being bullied, it is just as hard to experience the look of unfathomable despair on the face of David Long of Murray County, Georgia, whose 17-year-old son Tyler hung himself in a closet in the family home.

"I knew he would be victimized at some point in time," the father says, describing the indescribable. "He had a target on his back. Everyone knew that."

Sharing that agony is Kirk Smalley of Oklahoma, whose 11-year-old son also took his own life. "We're nobody," says the father, searching around for answers to why family complaints about school bullying had gone unheeded. "If it had been some politician's son, there'd be a law tomorrow."

This theme of parental difficulty in getting satisfactory responses from those in authority positions in schools is one of "Bully's" constant refrains. Adults are portrayed as clueless and ineffectual, reduced to either "kids will be kids" platitudes or hand-wringing sentiments such as, "This is an awfully complicated and difficult situation."

When it comes to showing what some kids go through on a daily basis, "Bully" concentrates on the situation of 12-year-old Alex Libby of Sioux City, Iowa. Ironically, precisely because the Sioux City school board takes the bullying problem seriously, it allowed filmmaker Hirsch broad access to East Middle School and to the buses where much of the bullying of Alex takes place.

Since the kids on the bus were used to treating Alex with impunity and because Hirsch shot with a small Canon 5D Mark II, no one held back from hitting and cursing Alex just because a camera was present, which is where the footage that gave "Bully" its R-rating comes from.

Hirsch clearly developed a strong rapport with Alex, a bright, aware kid with an awkward manner who seems to confide in the filmmaker more than in his own parents. Alex is desperate for friends, and he doesn't want to make waves, so he spends quite a bit of time trying to downplay the extent of his bullying, until Hirsch takes the unusual step of showing adults some of the footage he has shot.

For a variety of reasons, the two other teens depicted get less — and less effective — screen time than Alex. Though we hear from Kelby Johnson, a 16-year-old from Tuttle, Okla., who was ostracized when she came out as a lesbian, we do not see her being taunted. And young Ja'Meya Jackson of Yazoo County, Mississippi, who took her mother's handgun to her school bus to stop chronic bullying, is in so much trouble that we hardly hear from her at all.

"Bully" is not comprehensive — the more modern torments of cyber bullying are not much dealt with — and it can feel haphazard as it jumps back and forth between its subjects.

Still, the film's cumulative force is considerable, and, more than that, it shows the efficacy of a recent "I Stand for the Silent" campaign that encourages all kids to speak up when they see bullying taking place. Maybe, this film suggests, getting power to the powerless is not as impossible as it sounds.

kenneth.turan@latimes.com