It seems it was much worse, unfortunately. This article provides some summary information about the program.

While it's now widely recognized hitting children with objects is abuse, not discipline, it indeed was a common event in schools until relatively recently. And large groups of "captive" kids in boarding schools have probably widely been targets for predatory adults. But the rate of children dying at Indian residential schools was actually horrific-in the early years of the program some schools had half their students fail to survive. Many residential schools had attached cemeteries laid out even before the buildings were completed. Deaths were poorly reported, and stopped being reported to the government around 1917. However it's clear that shoddy construction, overcrowding, and malnutrition-often deliberately induced-were significant contributors to the death rates in these schools

Comparatively, it looks like from 1840 to 1940 in England and Wales the rate of death in children between 5 and 15 didn't reach 10 deaths per thousand. I couldn't find comparative data specifically for deaths in boarding schools over the same period, unfortunately. Maybe someone else can? I'd like to see it. But I'm pretty sure Eton never recorded half their students dying while in school.

For a deep dive into the subject, the report of the truth and reconciliation commission is required reading.

Not to discourage any further answers, but you should read /u/UrAccountabilibuddy's response to I am a young Canadian native and am being sent to a residential school. When would my schooling end and what would one experience during my stay?

the overwhelming majority of the children who were sent experienced long periods of deprivation including food scarcity and limited contact with friends and family, physical and sexual assault, and an unwavering intolerance for their culture, language, name, and experiences. In effect, if you were a Canadian First Nations, Métis, or Inuit child or teenager at a residential school, you'd experience adults using every bit of power they had over you to erase the things that make you ... you.