According to the film, 13 million U.S. students are bullied each year. (Image from The Bully Project)

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.