https://www.cbc.ca/news/canada/sask...eval-indian-residential-school-news-1.6078375
More unmarked graves found in Saskatchewan
More unmarked graves found in Saskatchewan
More than likely, if they were told anything, it was that they ran away. What is more likely is that it really was not questioned, because people were afraid of bringing attention to themselves, for fear of what else the authorities might do to them as punishment for daring to question.
Also, Pea-n-Me is right; it's global. Do some research on Kipling and "The White Man's Burden" to understand the flawed thinking that fueled it, even among people who had no personal opportunity to gain from it.