Police say that at around 2 p.m. PT, a 16-year-old girl was was walking on a pathway behind the school when a man approached her from behind and put his arm around her neck.
She screamed, and the man let her go and ran away.
Officers used a police dog to try and track him down, but came away empty-handed.
Police say the suspect is a white man in his mid-30s, who is approximately six feet tall and has a medium build and dark hair.
At the time of the assault, he was wearing a rust- or tan-coloured tank top, black shorts and sunglasses.
Anyone with any information is asked to call the Surrey RCMP at 604-599-0502 or, to make an anonymous report, contact Crime Stoppers at 1-800-222-TIPS.
Google map: Clayton Heights Secondary