A mob of schoolboys from three different schools turned on a 19-year-old picking his little sister up from school when he tried to stop them attacking a younger student.
The teen was attacked outside One Tree Hill College in Onehunga last week.
It was the fourth large-scale organised brawl or attempted brawl involving schools in the area - sparked by a Facebook photo of "a rude gesture" about one school's rugby jersey.
Police have taken a hard line against those involved in the earliest incident, charging two students aged 17 and 18 with assault for their part in a 60-student fracas between students from De La Salle and St Paul's colleges at Orakei Train Station last month. Since that brawl police have been called to three fights allegedly organised via Facebook.
Last Tuesday, the Onehunga teen - who was too fearful to be identified - was collecting his younger sister from One Tree Hill College when he said he was set upon by a group of up to 50 students.
"He saw a bunch of boys and he thought they were just playing, but when he had a proper look he saw they were beating up another boy," said the teen's mother, who also wished to remain anonymous.
"He tried to help the boy and get him out of the way, but the boys just turned on him and it was pretty bad - they kicked him in the face and he had to go to the doctor and have a week off work."
Her daughter tried to save her brother and was also kicked. Their 11-year-old brother witnessed the attack and is receiving counselling after having nightmares about the incident.
The schools involved have not responded to repeated Herald requests for comment.