A student at Melville Senior High School was given a juvenile caution and suspended after putting a laxative in a teacher's drink last month.

Palmyra Police station officer-in-charge Senior Sergeant Craig Collins told Fairfax Media that officers interviewed a 14-year-old boy on September 22 in regard to the incident, after the school reported the situation to police.

Senior Sergeant Collins said staff at the school had already identified the student responsible.

He said although the female teacher had not experienced any long term side effects, "putting a substance into someone's food or drink could result in dire consequences" and - while some may view the incident as "a joke" - offenders faced serious consequences