At least 973 Native American children died in the U.S. government’s abusive boarding school system, according to the results of an investigation released Tuesday by officials who called on the government to apologize for the schools. The investigation commissioned by Interior Sec. Deb Haaland found marked and unmarked graves at 65 of the more than 400 U.S. boarding schools that were established to forcibly assimilate Native American children into white society.