I’m assuming for most international students, school/college healthcare is mandatory, since any insurance from their home country would not most likely not be valid in the US. The OP is from Canada, so assuming they are also considered international (sorry don’t know), and the question would be if their insurance would be valid for a student residing in the US for 9 months of the year (may be valid for short trips into the US, but not extended stays), therefore most likely a mandatory purchase unless they can appeal and prove otherwise.