The hard work, dedication, and personal politics behind “rah rah rah!” and “sis boom bah!” go under the microscope in this engaging teen comedy. Torrance Shipman (Kirsten Dunst) discovers that being captain of her San Diego high school’s six-time championship-winning cheerleading squad is more complicated than she had imagined. Torrance’s parents want her to spend more time on her homework, her boyfriend wants her to spend more time with him, and she learns that the squad’s former captain stole some of their best routines from other teams — and that Isis (Gabrielle Union), captain of a top squad at a crosstown, inner-city high school, plans to fight back this year. To make things worse, when one of the cheerleaders is injured, Torrance is forced to replace her with Missy (Eliza Dushku), a cynical new kid who is involved only because the school doesn’t offer gymnastics. In the midst of this chaos, with the national championship around the corner, Torrance couldn’t have picked a worse time to fall in love with Cliff (Jesse Bradford), a classmate who cares a lot more about punk rock than school spirit. Dunst trained with a cheerleading squad for her role, though a double performed the more complicated stunts.