Red-haired pupils at a secondary school in South Yorkshire have been left hurt and bruised after classmates marked "Kick a Ginger Kid Day."
At least six red-headed students were reportedly attacked.
Parents have vented their anger online, after the incidents at Wingfield Academy, in Rotherham. They launched a Facebook group to discuss the attacks and some posted pictures of their children's injuries.
One mother told The Telegraph she would keep her 13-year-old son out of the school until she was assured there would be no further attacks.
She said: "My son rang me and said kids were kicking him, saying it was National Kick a Ginger Kid Day. He was scared so I went to get him out of school.
"My son's leg is swollen and there are bruises coming through."
The phenomenon - played out online, mainly in comedy videos and novelty merchandise - appears to stem from an episode of the cartoon show South Park.
A spokesman for the school told The Telegraph: “These deplorable acts, done in the name of singling innocent people out, have no place in our school and as soon as it was brought to my attention that such acts had taken place in our school, we acted swiftly to deliver a strong message.
"The pupils involved in carrying out these acts of violence have been strongly reprimanded and a school-wide warning has gone out that any future acts of violence, carried out in the name of discrimination, or any other reason, will be met with similar strong and decisive action.”