The attack and several others came to light during an oversight visit by the DA to Ndwedwe, about 60km north of Durban last week.
A spate of violent incidents, officials said, points to faction fighting in the district with some teachers allegedly mobilising pupils to settle scores against their rivals.
Isifiso Sethu High School was a flashpoint, with teacher unions blaming the provincial education department for the problems.
The principal, who only identified himself as Mr Khambule, confirmed that he was assaulted by a gang of pupils in January last year.
"I was away for the whole year while I was recovering.
"The problem was service delivery from the Department of Education. They promised they would renovate the school but didn't deliver," he said.
"I was cut on my face and on my head. They also stoned my car. I was assaulted by the learners and I was hurt. They were accusing me of chasing the teachers away. Three teachers had left the school. They were unhappy because of the state of the school and they focused their attention on me."
Khambule said he returned to the school once renovations started.
The DA's Mbali Ntuli said they had heard of another incident in which a teacher had been pelted with avocados by a gang of pupils.
Basil Manual, spokesman of the National Professional Teachers' Organisation of SA, said it was dangerous for pupils to be drawn into teachers' squabbles.
National Teachers' Union spokesman Allen Thompson said school security needed to improve.
"Currently security is not a priority. In most cases there is one security guard for more than 1000 learners and that is impossible for them to control," he said.
Education spokesman Muzi Mahlambi did not responded to requests for comment .
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