Police say several girls saw the man standing outside Magee Secondary School, lurking in the shadows off Maple Street, before classes started the morning of Friday, Jan. 31.
A short time later, the man walked in through the main doors and headed for the men's washroom near the high school's theatre.
"A student described the man as having his pants undone with his genitals exposed, as he watched the students that were seated in the rotunda," Sgt. Randy Fincham said in a written statement.
About 15 minutes later, he was seen leaving out the main doors.
Police want to identify the man, who is described as Aboriginal or Asian, 40 to 50 years old, and around f5'10" tall, with a medium build.
At the time of the incident at Magee, the man was clean-shaven and was wearing a black toque, a three-quarter-length black jacket, jeans and dark work boots.