Rebecca Riley, 28, was led away from Ravensworth Primary in Bromley in cuffs last June.
Teachers called the police over claims she had punched younger brother John, then nine, in the face.
But she says she was just restraining the schoolboy, who has autism, in a way she had been taught.
The Metropolitan Police dropped the probe just days later citing “insufficient evidence”, according to an email.
But she says she is still being ostracised in the community over the incident, even though she did nothing wrong – and wants a public apology.
Rebecca, who cares for her younger siblings, said: “I still feel really angry about it. That day was a nightmare.
“John was totally traumatised by it and so was I – and our mum.
“When they arrested me there were loads of parents there because of clubs after schools. It was horrible.
“I got death threats from parents and I was horribly bullied because of this.
“It made my life really difficult. I don’t like to go out alone because of this.
“I can’t believe they put me through all that because of a silly accusation that wasn’t a bit true.”
Rebecca was dropping John, now 10, off at school around 10am on June 9 when a teacher asked her to come inside, she claims.
The teacher said they had seen Rebecca punch her brother in the face.
But Rebecca said she was restraining John, who has autism and didn’t want to go into school, in a way she had been taught and used regularly at home.
Rebecca found the police were at the school when she returned to collect John and another sibling at 3:30pm, she says.
She was arrested then bailed to a friend’s house the following day, where she stayed for nine nights.
An officer emailed to tell her the case had been dropped on June 11.
But Rebecca was too frightened of things people in the community were saying about her to go home, she said.
Rebecca, who has eight brothers and sisters, said it was really hard being separated from her family.
John is too traumatised by the incident to go back to school so is being home schooled for now.
Rebecca said: “John gets really upset and he isn’t close to many people but he’s really close to me. I look after him a lot.
“it was awful being separated from him – I texted mum all the time because I missed them so much.
“They weren’t allowed near me or to speak to me.
“John doesn’t like going to school and was hitting me. When that happens I hug him tightly and stroke him until he calms down.
“The police could see from the CCTV that I didn’t hit him. I asked the school for an apology but they said they won’t.”
Rebecca was banned from the school’s premises after being arrested.
She appealed but a panel upheld the decision – meaning she still can’t drop John at school.
Education Trust for the 21st Century, which manages Ravensworth Primary, declined to comment.
The Metropolitan Police was approached for comment.
