At least 6,000 aboriginal children died while they were in the care of Canada’s residential school system, according to the country’s Truth and Reconciliation Commission.

Canada’s residential school system was established in the 19th century, and its last institution closed in 1996. They were government-funded and church-affiliated schools that housed aboriginal First Nations children, designed as civilizing institutions that would “kill the Indian in the child.

They have been condemned for their practices, which included isolating students from their families, sterilization, and exposure to physical and sexual abuse.

In 2008, Prime Minister Stephen Harper offered an apology on behalf of Canada for the conditions suffered by the children in the schooling system. However, Justice Murray Sinclair, the commission’s chair, said the figure was just an estimate based off the best available data. The commission heard testimony from 7,000 survivors of the system over five years.

"We think that we have not uncovered anywhere near what the total would be because the record keeping around that question was very poor," Sinclair said in a CBC interview. "You would have thought they would have concentrated more on keeping track."

Sinclair’s estimates, which were given in an interview aired Saturday, are significantly higher than previous estimates, which put the number of aboriginal children who died in the residential school system at less than 4,000.

Sinclair estimates that 25 to 42 percent of the aboriginal children who attended residential schools died during or shortly after their time in the school. About 30 percent of the country’s native children were placed in residential schools across Canada.

The new figures come shortly after comments made by Canada’s chief justice Beverly McLachlin, who on Thursday said the country had tried to commit “cultural genocide” against its aboriginal population.

"The most glaring blemish on the Canadian historic record relates to our treatment of the First Nations that lived here at the time of colonization," McLachlin said at a lecture.

The commission is set to release its report on Tuesday, which will include a set of recommendations for regional and national governments to help Canadians address their history. The government has offered billions in compensation to former residential school students.

The report is expected to recommend making residential school history a required part of school curricula across the country, and call on Ottawa to act against the substantial socioeconomic inequality that many aboriginal citizens face.

The commission’s work will culminate with four days of events held in Ottawa, starting on Sunday.