A 22-year-old teacher from a school in Adelaide's northern suburbs has been charged in relation to a child sex crime.

Detectives arrested the man on August 8 and he has since been stood down without pay.

9NEWS understands a letter was sent home to parents earlier this week.

It will be alleged the child was under the age of 14 years at the time of the offending.

The man has been charged with one count of aggravated incite a child to commit an indecent act.

He has been bailed to appear in the Elizabeth Magistrates Court on September 19.