According to a source, the incident happened during a Grade 12 Afrikaans class last week.
Pupils in class did not immediately react, but some were distraught after class, according to the source.
Steven Tait, chairperson of the school governing body, confirmed that the alleged incident happened on Friday.
“We take any incidents of this nature very seriously. The incident has triggered an internal investigation by the school and we’re also seeking external legal advice,” he said.