Thomas Robert Ackland, a former teacher from the Yorke Peninsula, has admitted to 14 child-sex charges.
The charges span over three years and include maintaining an unlawful sexual relationship with a child and aggravated communicating with intent to make a child amenable to sexual activity.
Ackland, 31, of Moonta Bay, initially pleaded not guilty but changed his plea during a pre-trial hearing in the District Court.
He was banned from Kadina Memorial School where he worked after his arrest in March 2021.
Victim impact statements are anticipated in the pre-sentence hearing scheduled for October.