It's understood the incident happened on Tuesday outside the school premises.
Police say the boy was stabbed multiple times on Tuesday.
The incident occurred at Forest Heights High School on Thursday morning.
Police said the accused stabbed to death the 14-year-old girl.
MPs were debating increasing levels of violence, drugs and sexual abuse in schools in one of two mini-plenary sittings in the National Assembly on Thursday.
Footage of the incident that occurred at Hoërskool Kempton Park last week has been shared on social media platforms.
Gauteng Education MEC Panyaza Lesufi visited a school in Kempton Park after a video showing a pupil assaulting another schoolboy went viral on social media.
Footage of the incident has been widely shared on social media platforms; it's unclear at when the incident took place.
It’s believed he was killed by fellow pupils after intervening in a fight at Eastwood Secondary School on Tuesday.
A grade 11 pupil from the Eastwood Secondary School in Pietermaritzburg was stabbed on Tuesday afternoon allegedly by fellow pupils after an earlier altercation.
Police conducted an inspection at schools ahead of the 2019 matric examinations.
Tshepo Mphehlo (14) was attacked with a pair of scissors by a fellow learner (15) at the Thuto-Tiro Comprehensive School on Monday in full view of his classmates.
On Tuesday, a grade nine pupil was stabbed by her schoolmate at the Reunion Secondary School in Isipingo, south of Durban.
Officers were called to the school on Tuesday after the two the girls got into a fight.
On Monday, a 16-year-old boy was stabbed to death at Hillcrest Secondary School.
A grade nine pupil was stabbed with a pair of scissors by a schoolmate on Monday. A pupil has been arrested after the stabbing.
It's understood the pupil was stabbed by a school mate with a pair of scissors at the Thuto-Tiro Comprehensive School in Sebokeng.
Two girls from got into a fight, leaving one of them in hospital. The next day, a group of learners and community members descended on the school demanding one of the girls be handed over to them, saying that they wanted to deal with her.
