I'm just trying to learn more about a really horrible thing in Canada's history.
Were these wound down over time or did the seizures of children continue right to the bitter end? Did the government ever step in to help out the childrens/families? Did it become any easier to get your kids back or did rights of Indigenous parents improve as time went on?
I'm not qualified to answer your question, but there is some info here: https://nctr.ca/education/teaching-resources/residential-school-history/
That is the National Centre for Truth and Reconciliation. That particular page has some info you might be looking for, and the website has a lot of additional info.
Additionally for up to date into, CBC has written some extensive coverage of the Truth and Reconciliation commission, and the inquiry into Missing and Murdered Indigenous Women.
Both of those inquires are recent and therefore too soon for this subs 20 year rule. I would highly recommend you read into current journalism on both these topics if you want some understanding.
There might be a lot of history about this topic, but it is not history, it's still happening today.