A report released this month found the search of the 15-year-old girl, known as Child Q, was unjustified and racism was "likely" to have been a factor.
Activists marched chanting "power to black girl Child Q" and carried banners saying "protect black kids".
The Met Police has apologised.
The girl's family is suing her school and the force, which said its officers' actions "should never have happened".
Speaking via her lawyers, the girl said she wanted "cast-iron commitments to ensure this never happens again" and thanked supporters.
Protesters marched from Stoke Newington Police Station to Hackney Town Hall with placards saying "no to racist police" and "hands off our children", while chanting "love for Child Q".
Jacqueline Courteney, who helped set up the rally, said: "I set it up because I'm a mother and I had that gut instinct a black child out there had been caused such harm, and that could have been my kids, or nieces and nephews.
"That's just not on, and there needs to be a way that we can demand change that is clear and obvious."
Ngozi Fulani, founder of charity Sistah Space which supports black heritage abuse victims, said she was "disgusted" by the incident.
"There's something in our system that doesn't see the humanity in black people, much less black children," she said.
"The police involved should be sacked."
A two-minute silence was also held in support of the girl.
During the incident in 2020, the girl was taken out of an exam to the school's medical room and strip-searched while on her period by two female Met police officers searching for cannabis, while teachers remained outside.
The girl's mother told the safeguarding review - by City of London and Hackney Safeguarding Children Partnership - that after the strip-search, her daughter had been "asked to go back into the exam" she had been sitting, with no teacher asking about her welfare.
Her family said the girl had changed from "top of the class" to "a shell of her former bubbly self", and she was now self-harming and required therapy.
The Independent Office of Police Conduct (IOPC) said its investigation was complete and its report was being "finalised".
It added three police constables had been served with notices last year advising them they were under investigation for misconduct, "over their roles in either carrying out the strip-search or involvement in supervising it".
Scotland Yard said the officers' actions were "truly regrettable" and it "should never have happened".