The incident took place in Jeonbuk, South Korea in March but only came to light recently, according to Korean broadcaster SBS.

According to the local teachers’ union, a parent complained to police after their child was asked to come up to the blackboard to solve a problem to which the child did not know the answer, making him “feel embarrassed”.

After an investigation, the Jeonbuk Jeongeup police station determined that no offence had been committed.

However, the teachers’ union said the lengthy investigation had a negative impact on the teacher.

The Jeonbuk branch of the Korean Teachers and Education Workers Union has called for stronger safeguards against parents’ use of “lawsuits and reports as a means of intimidation”.