Rejection reasons can be vague. This means that VO, for some reason, does not believe you are a bona-fide student.In rejection they gave this
am not satisfied that you will leave Canada at the end of your stay, as stipulated in subsection 216(1) of the IRPR, based on the purpose of your visit.
To get a better understanding of what issues the VO had with your application, you should order gcms notes.