The students were on a field trip at the time of the incident, which remains under investigation by the zoo.
The teens managed to get a close-up encounter with Humphrey, who was born at the Toronto Zoo in November.
Humphrey's older brother, Hudson — who currently resides at a zoo facility in Manitoba — made headlines this week when Prince Charles, on a tour of Canada with wife and Duchess of Cornwall, paid him a visit and even fed him.
Humphrey became an instant online sensation when video of his first steps was posted to Facebook by zoo staff. He is a prized treasure at the zoo: both of his siblings, who born at the same time, died shortly after birth last year.
Toronto Zoo officials said the teens could face serious consequences for their close-up with the cub.
"There have been, in fact, circumstances when people have been banned from the zoo, or have been charged with trespassing," said zoo spokeswoman Jennifer Tracey.
The zoo says it takes the health and safety of both its animals and guests extremely seriously — that’s why there are barriers in place, and signs warning visitors to keep their distance from the animals.
Click on the video above to see a full a report from the CBC's Charlsie Agro.