Auckland City Police arrested two students and charged them with assault. Aged 17- and 18-years-old, the students are being processed through the criminal court and may end up with criminal records.
Tensions between some students at the schools have continued to build after the fight and a third school has been pulled into melee, which started over a photo of one school's rugby jersey being given a "rude gesture" by a student from a rival school.
Inspector Vaughn Graham said police were taking a hard line with those involved.
"These young people are making a bit of an effort to get together to assault each other and they think it is okay in public places, which we are against and we are not going to let it happen," he said.
"The day before yesterday police had to send staff to three different places because there was going to be fights on the platforms."
Officers arrived to find students in the area "who were not there to catch trains".
Mr Graham said officers were still examining CCTV footage and online activity from all four incidents, and working closely with schools to diffuse tensions.
He said the schools involved had also handed down internal punishments to some students involved, too.
The schools have not responded to the Herald's requests for comment.
Mr Graham said Auckland Transport and Transdev Auckland, which operates the rail network, was also taking a tough line and would trespass anyone threatening the safety of other train users.
He encouraged parents to step in and talk to their children about online behaviour and the consequences of such actions.
"Someone made a rude gesture to a ruby jersey online, which is ridiculous when you think about what has happened to these young guys.
"The sad thing for these kids is they thought it was something worth fighting for, but I think they are likely to have a completely different opinion of that in five or 10-years time if they end up having a conviction, that's a serious price to pay."
