The incident happened at Mount Hutt College, Methven, and was described as "incredibly serious" in an email to parents sent today by principal Jack Saxon.
"Earlier today we had an incident at school where one student filmed another student, without their permission, with the intention of humiliating them, and then made this available to multiple contacts including contacts in our wider community," Saxon said in the email, provided to the Herald.
"This incident is incredibly serious and has the potential to significantly impact the wellbeing of the victim both now and into the future.
"We are liaising with the police and Netsafe about the matter and have been advised to direct anybody that has received the video to delete the material immediately."
Saxon said the offending student was suspend and would have to appear at a hearing before the Board of Trustees.
"Given the severity of this matter ... Further investigation is ongoing to determine whether the student acted alone and additional disciplinary action is possible depending on the outcomes of this investigation," said Saxon.
"At the end of the day our chief role as educators is to create a safe environment, both physically and mentally for the learners that come here.
"We will continue to do everything in our power, including utilising the most serious disciplinary consequences at our disposal, to ensure that we achieve this."