Sunday school principal at Dunedin's Al Huda Mosque Nurul Thiyahuddin said it was not first time the girls had been subjected to abuse because of their faith.
"There were early signs that were showing in school previously - like the girls were being verbally abused, there was lots of swearing and their complaints were not dealt with," she said.
"There were complaints to the teachers but nothing was done. These are little signs that if dealt with early, may not have escalated to what we have seen. I felt it's a shame - it could have been prevented."
A Change.org petition is calling for the school to address the attack, and for people to unite against hatred and bigotry.
It had already gathered more than 50,000 signatures.
Thiyahuddin said the assault had shaken Dunedin's Muslim community.
"We're very saddened, very distraught, very alarmed by what's happened," she said.
"We've always prided ourselves that we're in a very diverse city. People are generally very, very welcoming and for this to happen in Dunedin is a big shock to us."
However, Thiyahuddin said she had also faced Islamophobia.
"Being a Muslim woman, we are advertising our faith. It's out there for everyone to see.
"I have had abuse hurled at me from passing cars. I am a dentist and I've had patients decline to be treated by me based on race. I have faced that situation, but not in a physical way like this - this is totally unacceptable."
There were efforts and promises to do better and improve tolerance after the Christchurch terror attacks.
But since 2019, the momentum had died down.
Thiyahuddin said she wanted more to be done to teach New Zealanders about other cultures and faiths to improve tolerance, and the best place for it to start would be in the schools themselves.
"We need an ongoing effort because we're all out there and it's not just Muslims, it's people of other faiths and races as well. And I don't just want other people to understand Muslims - it's vice-versa. I want our Muslim children to also understand other faiths. Where there is understanding, you can accept each other and live together."
She hoped last week's ugly incident would provide a wake-up call and an opportunity to teach greater tolerance and understanding.
Police said the offenders had been identified and officers were investigating.