Nothing sells better in certain situations than puritanical hysteria, so calling this shocker about two 13-year-old girls in Los Angeles a must-see for parents, as I’ve heard some colleagues do, isn’t all that different from urging them to read the tabloids—and if exploitation is what parents are looking for, Larry Clark’s Bully puts on a better show. I’m not questioning the sincerity of the filmmakers: director Catherine Hardwicke wrote the script with costar Nikki Reed when the latter was still 13, basing it on her experiences, and there are persuasive performances by Reed, Holly Hunter as her struggling, hapless mother, and Evan Rachel Wood as the other girl, who falls under Reed’s influence. But they often seem more bent on titillating or harrowing us than on helping us understand the characters. With Jeremy Sisto and Deborah Unger. R, 100 min.