Young Writers of Canada (http://youngwritersofcanada.ca/htmdocs/contests.htm) is now accepting entries for the annual Young Writers Short Story/Creative Writing contest. The contest is open to youths ages 7 - 18 and the deadline is March 23, 2012.
Each fall, Polar Expressions (http://www.polarexpressions.ca/StudentContests.html) hosts two contests (one for poetry and one for short stories), both of which are open to Canadian students in kindergarten through grade twelve. According to the website, "Over $10,000 is awarded in cash prizes to schools and students who participate!" The deadline for entries is November 21 if submitting by regular mail and November 30 if submitting by email or fax.