According to the SA Police figures obtained by The Advertiser, 42 sexual assault offences were reported in schools last financial year with the crimes including rape, attempted rape, unlawful sexual intercourse and indecent assault.
A total of 204 such offences have been reported in the past four years with 15 sexual assault offences during "core" school hours on Monday to Friday between 8.30am to 4pm and a total of 78 during those hours since 2004-05.
Department chief executive Chris Robinson released six pages of incident reports from the school for 2006, 2007 and 2008, detailing shocking behaviour by its students, ranging from verbal to physical sexual abuse.
The incidents included boys exposing themselves in class, pushing girls to the ground and simulating sex, pulling down other students' pants and underwear, and violent sexual language and threats to teachers and students.
Once a student even "brought a plastic penis to school and sexually harassed another student".
Robinson said the incidents "are of significant concern".
Education Minister Jane Lomax-Smith also termed the trend "very serious" trend.
"The issue at primary schools is significant, because those behavioural issues might raise matters of child protection," News.com.au quoted her, as saying.
She blamed increasing exposure to inappropriate forms of media for the disturbing trend.