The name of the school cannot be published.
The principal said in the letter that parents of the student had been consulted and the staff member stood down.
They said there was no current risk to students.
Police confirmed an investigation into an allegation of grooming by a teacher at a south-west Sydney school had begun last month.
They arrested a 27-year-old man at an Eagle Vale home yesterday.
He has been charged with grooming a child.
He appeared before court yesterday, where he was formally refused bail.
The man will return to court on July 11.
