There are indeed unmarked graves at residential schools in Canada. Whether these include mass burials or not is currently under investigation. The New York Post is incorrect in claiming that "academics" have "debunked" the Kamloops mass grave.
750 unmarked graves
The CNN article reports that
More than 750 unmarked graves were discovered at one such school.
This refers to a communal graveyard on the grounds of Marieval Residential School in Saskatchewan which allegedly had headstones removed by the Catholic Church. This was not immediately determined to be a mass grave; it is currently unknown. In October 2021, the community was able to match 300 of the unmarked graves apparently to indigenous members of the local Catholic church. In January 2022, Canada agreed to release Marieval Residential School records which will show when children died at the school and whether they were buried without headstones.
215 unmarked graves?
The NYPost article declared
‘Biggest fake news story in Canada’: Kamloops mass grave debunked by academics
This refers to a different case, Kamloops Indian Residential School. Against the claim of 215 burials there, a retired economics professor named Frances Widdowson has cited the aggressive counterclaim of
“not a single known victim, not a single identified murderer, not a single grieving parent looking for a child who went missing while attending a residential school, and not a single body.”
Widdowson's article shows that a small number of graduates of the school claim they remember forced abortions or murders, but that none of their claims have been matched to any missing children. She also discusses the vagueness of the claim of unmarked graves.
This is a reasonable objection to the news media's initial report of a "mass grave," which The Guardian later revised to "unmarked graves" (as pointed out by AmiralPatate -- thanks). Widdowson shows that the revised claim of "unmarked graves" still lacks key evidence such as names or dates.
However, she goes beyond simply raising concerns about the reliability of individual testimony, in claiming that she has uncovered a "moral panic" similar to "the satanic abuse panic" which renders the claims of mass graves entirely baseless and fraudulent. I looked into the sources Widdowson cites and found that she mistreats her sources. Specifically, she approvingly cites
three indigenous staff members [who] are featured in the 1962 CBC documentary The Eyes of Children (now considered, without explanation, to be a “propaganda film” by The Fifth Estate) ... The Eyes of Children offers a stark contrast to the macabre tales being told: footage of children enthusiastically crowding around one of the priests, playing sports, and being taught dancing by a nun. Three indigenous teachers, Michel, Paul, and Caron, can be observed giving classes and providing training in a machine shop.
Widdowson is aware of the 2000 book Behind Closed Doors describing abuse at this school, and mentions it no fewer than five times in her essay, but she doesn't note that it explains the context of this propaganda film. Namely, the school fiercely censored all discussion of abuse there, even in children's letters home. I will quote from a summary of the book:
One way for students to resist was through writing letters to their relatives. One student,
tried to write letters home to his parents to tell them the Oblates were not treating him well.
After the Oblates discovered that the student had criticized them he was no longer allowed to
write letters home. Another student remembered that the teachers would write a letter on the
black board for the student to copy, and they were not allowed to add anything else or they
would not send it. She remembered it well, “it said “Dear Mother and Father, How are you? I
am fine” and then they left a blank for the name.
Of course any film made at the time for the purpose of promoting the school would show smiling children gathering happily around priests. Behind Closed Doors also explains that only boys were allowed in the machine shop, while girls were made to sew the boys' clothes and change the bed linens of the priests (and, incidentally, used sexually segregated textbooks that focused on preparing them for giving birth and raising children). Despite this, Widdowson demands some "explanation" for why the film is considered a propaganda film.
At the risk of beating a dead horse, here are some details from the same summary about what life was really like at the school:
The food the students received at the KIRS was less than satisfactory. One student wrote, “if the milk was not sour, it was burnt.” There were many complaints about eating porridge all the time which was old, without milk or with sour milk. They would also receive mush that had big lumps for lunches or dinners. The students had to eat all their food or they had to sit there until they did. Students would break into the kitchen and take food because they were not given enough to eat. One student lost some of her teeth because of the food. She lost some of her teeth because the young children who cleaned the beans and would not wash away the little rocks in them. The KIRS staff ate at a different table and had different meals than the students. Many students account that the priests and nuns had good food. Students were not only malnourished at the school but disciplined through physical punishment.
Bed wetting was treated in a harsh matter at the KIRS. Students who wet the bed had to wash their own sheets and if you were a boy this was particularly humiliating because you had to cross over to the girl's side to the laundry room, which allowed everyone to know you were a bed wetter. The staff would also take the student's sheet and wrap them around their head and make them walk down the hall past other students, who would tease them. Bedwetting was a type of physical and emotional abuse. Other students as well experienced emotional abuse at KIRS.
The emotional abuse described by the students at the KIRS has caused detrimental effects to many students. Many survivors have trouble expressing their emotions. A student summarized the impact residential school had on his life, and he still cannot show his inner feelings towards family or for people in pain. A common feeling of the students was they became isolated. Many are angry because it has affected their relationships not only with their children and spouses, but their grandchildren. Many students lost strong connections with their parents and communities.
Sexual abuse at the KIRS could be under recorded due to the shame associated with it
and privacy of the students. Male and female students were both subjected to sexual abuse;
however, there is more testimonial evidence that female students were more likely to be sexually
abused. Many girls grouped together in order to avoid sexual abuse. A female student commented that her female friends all “hung out together” and would stay in groups. In this
particular case there was one staff member described as a “big tall guy,” and named Anthony
who worked in the basement and was known to sexually molest girls.One female student
recalls her sister telling her to stay away from him because, “he [had] these girls, he [got] them
by themselves and he sexually [molested] them downstairs in the basement.”
I excerpted these paragraphs from an undergraduate senior thesis which goes on for several more pages about other incidents at the school. It does not mention any murders, but it notes that many students tried to run away from the school.
It beggars belief that Widdowson's intention was to write a fair analysis of possible mass burial when she cited Behind Closed Doors no fewer than five times, but completely ignored the book's documentation of widespread abuse. (She uses it only as negative evidence against claims of murder, although of course unmarked burials could also result from neglect.)
In conclusion, Widdowson's article raises some legitimate concerns about the claim of a mass burial of 215 children which was quickly repeated by the news media and politicians, but I find her counterargument is extremely biased in its treatment of sources. Furthermore, the case of the 750 unmarked graves shows that unmarked burials at residential schools did happen. The New York Post's claim that "academics" have "debunked" the Kamloops mass grave is false.
I think it is too early to determine whether there are mass graves of indigenous children in Canada, but there are certainly unmarked graves at residential schools.