Grace knew she was in trouble, but had no idea what she had done wrong.
Last week, a teacher at Bentleigh Secondary College pulled the 16-year-old out of class and took her to a corridor, where her twin sister Tahbisa was waiting.
The students, who were born in South Sudan, were ordered to take out their braids by the weekend.
"We were told that our hair doesn't represent the school," Grace says. "It was a real shock."
The twins have worn braids since they were babies and say their state school is attacking their African culture.
"It's not a problem and it doesn't affect our education. They are asking us to look like everyone else," Grace said.
The students are refusing to take out their braids and have accused the school of discrimination.
The school tried to justify its position by saying that white students who have returned from holidays in Bali have also been asked to remove their braids or cornrows.
"That's different," Tahbisa says. "That's cultural appropriation."
She said braiding her hair made it healthier and easier to manage.
"It's a protective style. It looks good and it keeps our hair growing. Your hair is your crown, it is about embracing yourself, accepting yourself. It is part of our identity."
Bentleigh Secondary College principal Helene Hiotis said the request had nothing do with the students' background.
"Our school has a strict uniform policy that has been in place for 10 years and is regularly ratified by the school council," she said.
"The policy applies equally to all students. We are incredibly proud of our uniform policy which plays an important role in developing a positive and proud school culture."
Hair continues to be a battleground for black students, despite school uniform policies having to comply with anti-discrimination legislation.
This week in Mildura, 14-year-old Caleb Ernst was threatened with expulsion from St Joseph's College if he retained his dreadlocks.
The Year 9 student, whose father is Nigerian, said his hairstyle represented his heritage.
"I need to be true to myself," he said. "This is how I keep my hair tidy. I used to have an afro but I find dreadlocks easier to maintain and I feel more comfortable."
He is refusing to change his hair and will instead move schools.
"Not many people around here have their hair like me, they don't know what it is like," he said.
Grace and Tahbisa have been inundated with messages of support after posting about their experience on a Women of Colour Facebook group.
One young woman said she would help them lodge a complaint with the Human Rights Commission.
The girls have attended the school since year 7 and say their braids have never been an issue before.
They are diligent students, who have aspirations. Tahbisa wants to be a political scientist when she grows up and Grace is interested in psychology.
Over the weekend, as the twins juggled VCE assignments, they re-read their school's policies, which are printed at the front of their diaries.
"The policy says diversity is valued," Grace says. "The school is going against its values."