CAN I EXTEND MY STAY AS A STUDENT?
If you have a Study Permit, you can apply to extend your stay as a student over 6 months through a Canadian visa office within Canada.
If you do not have a Study Permit you can extend your course or enroll in another course as long as you are not studying for longer than 6 months in total. If you would like to extend your studies in Canada beyond 6 months and do not have a Study Permit, you must apply for a Study Permit at a Canadian visa office outside of Canada.
More information regarding an application for changed conditions or extending your stay in Canada as a student can be found here, http://www.cic.gc.ca/english/information/applications/extend-student.asp