A high school student from Guelph has been charged after police were called to a south-end school on Thursday.
Officers said a noxious substance was sprayed outside the school.
They said a 17-year-old student had been sitting in his car when he was approached by another teen and sprayed in the face with a substance similar to pepper spray.
The victim told police they were in pain and experiencing shortness of breath. A staff member who helped the student also suffered symptoms due to secondary exposure.
Officers located a 17-year-old boy at his home later that afternoon and arrested him for assault with a weapon, carrying a concealed weapon, possessing a weapon for a dangerous purpose and administering a noxious substance.