They said they had experienced discrimination themselves and felt it was important to speak out in support of Al Jamaa and her friends.
"We wanted her story to be heard, we wanted it to reach to as many as people as possible."
They said they were "very disappointed and upset" at the school's handling of the incident and wanted the attackers suspended and a formal apology issued.
"All the school is doing right now is just talking and talking and they are not giving any action. They haven't even made a public apology to Huda and her friends and we think that's very wrong.
"The principal has decided not to comment any further because the police are handling the incident, but even with that, we think that shouldn't have stopped her from admitting that this incident was sparked from hate and discrimination."
Otago Girls' High School principal Bridget Davidson said she could not say if, or how, the students involved were disciplined after an investigation, but said strong steps were taken.
She said the school had no tolerance for unkind comments, racism, bullying or any other form of discrimination and she was sorry the tragic event happened on school grounds.
In a statement on the Otago Girls' High School Facebook page, the school board's chairwoman, Lyn Hurring, said the board had last week completed its formal disciplinary processes, after an investigation.
Hurring said she was confident appropriate steps had been taken after an incident where one of the school's students was concussed and her hijab forcibly removed on school grounds.
She said the board could not say if, or how, the students involved were disciplined, but she was confident the incident was handled appropriately.
The Ministry of Education told Morning Report in a statement that the formal disciplinary process in relation to the incident had been completed but New Zealand privacy requirements meant the outcome could not be disclosed publicly.
"However we know that the school has kept their parent community updated about the processes they followed and that they have supported all those involved throughout," the statement said.
The sisters who started the petition said they were amazed at how it had taken off and the support of an international celebrity like Hadid was helping them to keep going and ignore some of the hateful messages they were receiving.
"It was very shocking for us to see such a celebrity even look at it, read it, but Bella is known for stuff like that; she's always very supportive of Muslims and the hijab.
"It's our honour that she posted it and she had the time to read it."
They said despite receiving some negative comments from people after launching the petition, the vast majority had been supportive.
Their own experiences of racism ranged from being sworn at in the street and accused of carrying bombs, to being passed over for jobs once interviewers realised they wore hijab, they said.
Any donations directed to the petition, which remains online, will go towards change.org and not to Al Jamaa or to the petition's organisers.
