I dont know such school around... And i am working with fireworks for my 14th season this summer.
I suggest you to get your certification from the Explosives Regulatory Division of Canada. You'll get info there:
http://www.nrcan.gc.ca/mms/explosif/edu/edu_displayA_e.htm
After that, the way i know is to learn it from experienced workers. To do so you must contact a company to do some fireworks with them. And learn from practice.
Remember that you will need too the "permis général des explosifs" (sry dont know it in english) from the Sureté du Québec wich is 31$ and can be obtained at the Parthenais prison in Montreal at the "Bureau des permis"