The young teacher, whose name is known to TimesLIVE, had resigned with immediate effect, said the principal of Bishops in Cape Town.
Guy Pearson said in a statement on Friday evening: "Bishops is currently investigating allegations that there has been serious misconduct by one of its teachers. The teacher has resigned with immediate effect and the school is in the process of conducting a full investigation.
"The school takes this matter extremely seriously and requests the public to respect the dignity and privacy of those concerned."
The teacher, who a sports coach, as well as holding other positions at the school.
The former part-time model married her long-term boyfriend in 2018. Her social media profiles have been deleted.
The college (high school) at Bishops has an enrollment of about 735 boys, a mixture of boarders and day pupils.
