The three suspects, whose identities were not released because of their ages, were booked Wednesday and released to their parents. They could face misdemeanor charges, but it was unclear when the case might be submitted for possible prosecution, Whitmore said.
Four girls and three boys reported that schoolmates shoved or kicked them on Nov. 20 at A.E. Wright Middle School in Calabasas, an affluent suburb of Los Angeles.
No serious injuries were reported. Most incidents involved a single person kicking a student's shoe or leg, but one youngster was bruised when three or four boys confronted him at once, said Donald Zimring, superintendent of the Las Virgenes Unified School District.
He may have been kicked in the groin or head while on the ground, although accounts differ, Zimring said.
"Any time a youngster gets hurt because of a thoughtless act ... there ought to be consequences," Zimring said.
Assemblies were held Monday at the school to discuss the incident.
Investigators said the attacks apparently were inspired by a 2005 episode of "South Park" that parodied racial prejudice by having the character Cartman incite a hate campaign against freckled, red-haired "ginger kids."
The episode apparently inspired the 13-year-old to send his friends a Facebook message declaring "Kick a Ginger Day," Zimring said.
Most students ignored or deplored the message and some sent "Protect a Ginger Day" counter-messages, but a dozen or so students apparently acted on the joke, Zimring said.
The students involved were facing discipline ranging from picking up school trash to five-day suspensions. None will be expelled, Zimring said.
"The youngsters involved understand that this was not acceptable, and they have made various forms of apology and contrition," Zimring said.