The man, who was in his mid-20s, was declared dead at the Belvedere School on Sunday at around 1.20pm, according to Benoni City Times.
Benoni police had reportedly opened an inquest docket for investigation.
Neither the school nor the local police could immediately be reached for comment on the incident.
This after a nine-year-old boy apparently hanged himself with a cord from a raincoat at the Georgedale Primary School in Mpumalanga earlier this year.
The boy had been found under a desk with the string around his neck, according to the SA Press Association.
The boy was reportedly still alive when he was taken to a clinic, but later died.
Police had suspected no foul play in the apparent suicide.
Following a spate of suspected suicides, the South African Depression and Anxiety Group (Sadag) urged anyone at risk of being suicidal or who was feeling depressed, to phone its suicide crisis helpline on 0800-567-567, and speak to a counsellor.