The KwaZulu-Natal education department is investigating allegations that six male teachers at a Durban high school are involved in sexual relationships with pupils, the Mercury newspaper reported on Wednesday.

The pupils were as young as 15 and in exchange for the sexual relationships they allegedly received money and alcohol.

The department's Umlazi district director Mlungisi Ntombela said about 20 female pupils arrived at his office on Friday to report that teachers had frequently had sex with other female pupils in the science laboratory.

The whistle-blowers said the teachers also consumed alcohol with the girls, and would give them R100 after sex.

Ntombela said some of the girls had been romantically involved with the teachers.

He and other officials visited the school on Tuesday to investigate further.

There was also an allegation that one pupil dropped out of school after being impregnated by a teacher.

A team had been set up by the department to investigate the allegations.

The SA Council of Educators chief executive Ricky Brijraj said 18 teachers were struck off the roll since the start of the year for unethical conduct, which included sexual violence against pupils.

He said the names of offending teachers would be published on the council's website in June.