Canada

Most of those responsible are probably dead—the Kamloops school closed in 1978 after ~85 years of use, and there would have been more deaths earlier in the school's existence. Assuming staff members were at least 20 years old, the youngest of them would now be in their late 60s, and the testimonies of the surviving students would be more useful in bringing them to account.

Whether the remains need to go home to their families is something the families have to agree upon. Some might prefer that the remains be left undisturbed. Religious beliefs may factor in, and may differ between tribes—it's unlikely that all the victims were local.