The victim lay on the field until he was eventually helped off the field and taken to hospital. He has since been discharged and is now recovering from his injuries at home.
Posts on social media referred to the boy's wound as a "very deep cut".
"Doctors said it's actually down to the bone."
Kyle Kirsten's father Glen, who met with police this morning, said he was satisfied the incident was a prank that "has gone a bit wrong".
"My son is fine. He has an injury but that will heal," he told the Herald.
"My wife and I are more worried about what's going to happen to the girls, you know, the repercussions.
"We all have a chuckle about it. I mean we probably shouldn't, but something far worse could have happened."
Glen said his son had made a statement to police, but he was also concerned about the outcome of the prank for the Diocesan schoolgirls.
"We all do silly things, you know."
His father didn't expect his injuries would prevent him from completing end of year NCEA exams, which start on November 9.
But while the victim's family wanted the incident to blow over, Hamilton Boys' High School principal Susan Hassall told the Herald she hoped charges are pressed.
"I think we need to send a strong message to young students that such reckless behaviour won't be tolerated."
The girls weren't invited on to school grounds and she called the speed at which they were driving the bikes "very dangerous".
"I'd call it more than a prank to be honest."
Waikato Police Senior Sergeant Ray Malcolmson said the prank happened just after midday yesterday and police rushed to the school after receiving a call from ambulance staff.
"There was a collision with a bike and a student on the school grounds. The student has suffered moderate injuries and has gone to hospital," police said.
Waikato road police senior sergeant Pete van de Wetering said they retrieved a Go-Pro camera that had come off one of the girls' helmets.
He said the six girls rode in pairs on trail bikes through the school grounds and on to the sports field amid large crowds of students during lunchtime.
"It was a foolish thing to do, riding at that speed through the grounds with that number of students around," he told Fairfax.
Van de Wetering said the 17-year-old boy was playing a game of soccer with a large group of students on the sports field and did not see the motorbikes coming.
He ran into one of the bikes and suffered a deep wound to the leg and was taken to hospital by ambulance, where he required at least a dozen stitches.
He had since been discharged.
Police are also reportedly looking at possible charges relating to the manner of driving.
Van de Wetering said the girl riding the motorbike that struck the teenage boy would be culpable.
"There will be some type of enforcement to the other girls for the manner in which they were riding the bikes."
None of the girls were licensed to drive that type of bike on public property.
"While it was on school grounds it is public property and if they are going to ride in a public place they need to have a suitable motorcycle licence," he told Fairfax.
"Police will be considering charges - there must be some accountability given the risk of injury, which has been demonstrated in this case.
"While we understand it was a prank and a bit of spirited excitement by the girls, if there has been an injury, like there was in this case, there must be accountability."
Police officers would be speaking with the girls who were all 17-year-old girls from Waikato Diocesan School for Girls on Thursday.
Waikato Diocesan principal Mary Curran confirmed school authorities were helping police.
