The pupil from Modiri Technical High School claimed to have been raped earlier this week, said Cosas secretary Khulekani Skosana.
The same teacher was alleged to have harassed other girls at the school.
“After she opened a case, we decided to have the march,” said Skosana.
Police Captain Johannes Maheso confirmed that a case of sexual assault had been opened against the teacher.
“At the moment, no arrests have been made,” said Maheso.
Skosana said by 9am, at least half of the school pupils in the area had gathered at a park next to Solomon Mahlangu High School.
“We are marching to the school to check to see if the teacher has been suspended. From there we are marching to the two police stations to call for the police to act, and then we are going to the taxi rank in Wonderboom.”
He explained they were going to request taxi drivers to give a discounted taxi fare to school pupils.
“When you are wearing school uniform, taxi fare should be less by at least 50 cents or R1,” said Skosana.
Maheso said police were not aware of the march.