How long ago were these schools running?
Was it before antibiotics, or did it overlap with any massive epidemics in North America?
It was a while ago. And yes. Several heat waves in Canada too at the time amongst other events.
The removal of children from their aboriginal homes started in 1870 I think and happened in all provinces except maybe Newfoundland/Labrador. The justification was that they were heathens being raised without religion and according to their own culture. Once the children were deemed to be of sufficent religiosity, they were adopted out of the residential schools, usually to non-aboriginal homes. The last residential school closed in 1996 in Canada. It’s a shameful period in our history, and one that happened in other countries, suggesting it was systemic and a coordination between governments and the Catholic Church.