The crash happened around 9:30 a.m. ET on Valcartier Boulevard.
Provincial police officers said it appeared the 53-year-old male driver lost control of the bus after suffering a heart attack, but have yet to confirm whether a medical problem caused the crash.
The Mont-St-Sacrament high school students aboard the bus were treated for minor injuries.
"All these students were transported to hospital. The injuries are minor. We're talking about injuries to the neck and back, nervous shock as well, but it doesn't initially seem serious for the students," said Marco Labbé, one of the school directors.