Police officers and detectives, along with the police helicopter and the dog squad were called to the scene, however the offender was not located.
The victim required medical treatment following the attack, and is recuperating at home.
Detective Senior Sergeant Brett Batty described it as a "vicious and cowardly attack with very sinister undertones".
"We are following a number of lines of inquiry but seek assistance from the community to locate and apprehend this offender. I am appealing to any members of the greater Warkworth community who recognise the description provided, or who may have observed suspicious activity in or around the Mahurangi College campus either on the night in question or in the days leading up to it, to contact me immediately."
Anyone with information should contact Senior Sergeant Batty at the Orewa Police Station on 09 4265 871.