?? So the teacher's union is going back for more than a century to get at someone who was in favor of 'home schooling'! Then again the term of 'residential schools' may be a code term for something different from what it appears.
Otherwise it is hard to find where he has been 'controversial' except for changes in accepted mores over time, ie expansion into native lands, treatment of Qubec armed rebellion etc. If so, then his statues may be in danger up there.
From the Canadian Encyclopedia:
“Residential schools were government-sponsored religious schools established to assimilate Indigenous children into Euro-Canadian culture.”
Quite apart from this issue, Macdonald was a colourful character: an alcoholic, he once publicly vomited in the House of Commons, claiming “It’s not drink that makes me sick but the rantings of my honourable opponent!”.
He later ordered the execution of Louis Riel, the leader of a Metis rebellion against Canadian rule, resigned from office due to the Pacific Scandal (he awarded a lucrative railway contract to a construction company from whom he demanded a large sum of money) and was then re-elected Prime Minister.
In the video accompanying the story he is burned in effigy by protesters!
The negatives: separated children from their parents, kinship network and culture for extended periods of time, intentionally effaced native languages and the transmission of native cultural and religious traditions.
The positives: separated children from extremely unsafe environments (childhood mortality rates "back home" exceeded 50%), saved children from native cultures which featured extreme cruelty, slavery and misogyny, introduced children into participation in the wider civilization, made their survival and (arguably) their peoples' survival possible.
So, a mixed bag.
Now it is non-PC to refer to it as anything other than "cultural genocide."