That is actually a great question.
I believe the Inuit who have succeeded academically have an association with the curriculum that they're based in. They've adapted to the English curriculum incredibly well, to the point where they have a full understanding of their education and therefore have graduated.
Those, for example, who may have flown in.... This is mostly Iqaluit-based because it's a very multicultural city on its own. For an example, somebody who has Inuktitut as their mother tongue and moves into Iqaluit and goes to high school there can have an incredibly difficult time because they do not understand English at a full level. They cannot, therefore, graduate academically because of that language barrier.
I believe those who do succeed academically have that bilinguality and understand English enough to graduate in the Alberta system. In smaller communities, the majority of the teachers of the academic classes like math and science are also anglophone and speak English. From a smaller community's perspective, many Inuit kids probably do not like that class, don't go to school or skip that class because, again, they don't have that English understanding and, therefore, cannot relate to it culturally.