The South Australian Department for Education is investigating a presentation delivered to year 9 girls in a regional high school that allegedly referenced bestiality as being accepted by the LGBTQIA+ community.

Female students said teachers at Renmark High School told them to leave their lessons and attend a presentation in a separate classroom.

Students who attended the presentation on March 22 say two staff from the Headspace centre in the neighbouring town of Berri introduced a "third-party" presenter who facilitated an hour-long presentation focused on relationships.

Parents said they were not notified about the presentation, nor was it consented to.

Students said they were left unsupervised for the duration of the presentation.