A five-year-old asylum seeker was urinated on by a group of Nauruan boys and asylum seeker girls have been sexually harassed at school, a former teacher says, saying many parents are too scared to send their children to school in 2016.

The claims are backed by asylum seeker children who report that Nauruan students threaten them with knives and teachers routinely swear at them. One Iranian boy reported his female Nauruan classmates offered sex for money.

In one alarming allegation, outlined in an official incident report sighted by Fairfax Media, a group of children were hit with a wooden ruler for being late to an exam.

It has been six months since the Australian government closed the detention centre school and forced child asylum seekers into Nauruan schools, where classes are taught in the Nauruan language and teachers are frequently absent.