Three boys were booked on suspicion of bullying or kicking red-haired students at a US middle school when a Kick a Ginger Day prank inspired by a South Park episode got out of hand, authorities said.
A 13-year-old boy was detained last week for investigation of threatening to inflict injury by means of electronic communication - essentially, cyberbullying.
Two 12-year-olds were booked for battery on school property, Los Angeles County sheriff's spokesman Steve Whitmore said.
The three suspects, whose identities were not released because of their ages, were booked and released to their parents.
They could face misdemeanour charges, but it was unclear when the case might be submitted for possible prosecution, Mr Whitmore said.
Four girls and three boys reported that schoolmates shoved or kicked them on November 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, Mr Zimring said.
"Any time a youngster gets hurt because of a thoughtless act ... there ought to be consequences," Mr Zimring said.
Assemblies were held 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, Mr Zimring said.