The deaths of the kids is bad but probably not quite as bad as it seems because as wilbur says child mortality was much more common back in the day. That's not defending anything just pointing out facts and putting things in proper perspective. It would be interesting to know the mortality rate of residential school kids vs the average rate throughout the decades.
I expect the rates would be higher in the schools, possibly a lot higher but we don't know that for a fact yet. Eyeball is right about the efforts to downplay and ignore this for years.