There are student fares ex-HKG to most longhaul destinations available from TA/CX res. They are usually cheaper and booked into a higher booking class compared to year-round fares of the same period of validity. Needs to be age under 30 with a copy of student ID.

Did a quick search... for YYZ departing in Aug, the student fare should be around HKD12K for a 9-month ticket (M class), around HKD13K for 12-month ticket (K class).