In Canada, the Indian residential school system[nb 1] was a network of boarding schools for Indigenous peoples.[nb 2] The network was funded by the Canadian government's Department of Indian Affairs and administered by Christian churches. The school system was created for the purpose of removing Indigenous children from the influence of their own culture and assimilating them into the dominant Canadian culture, "to kill the Indian in the child." Over the course of the system's more than hundred-year existence, about 30 percent of Indigenous children (around 150,000) were placed in residential schools nationally.:2–3 The number of school-related deaths remains unknown due to an incomplete historical record, though estimates range from 3,200 to upwards of 6,000.
You can read about the Canadian Indian residential school system and understand why the mother is so upset about it