Canada

Sure, but if you read the article attached to the citation for the 1884 shooting, it sounds like it was an unhinged head teacher angry that the lady teacher didn't want his dick. It was an attempted murder suicide, that happened at a school, because that was their work place. The head teacher fired 3 shots from a revolver, wounding the teacher, then took his own life. I think these weren't on the Mass Shootings list because they don't meet the criteria for it.
From the wiki page I linked in my OP:

This is a list of mass shooting and shooting sprees in Canada. Shootings with four or more victims are included on this list, excluding perpetrators.

Most of the school shooting list seems to be attacks targeting specific victims...and in one instance a door...
At least until the back half of the 20th century. From 1900-1999 there's 43 instances. Of those only 7 hit the required 4+ victims excluding attacker. All but one are post 1950. The one was 1902.
Even post 2000 the majority of instances are things like:

A student fired a rifle in a classroom at Lake Melville School during show-and-tell, hitting no one.

A student fired a gun on a school bus as he was being driven to school. The student and his friends convinced other occupants the gunshot was harmless and went to school still possessing the firearm. The school's vice-principal subdued the teenager at school and confiscated the firearm.

Or very much targeted attacks:

62-year-old Erhun Candir killed his wife, 47-year-old teacher Aysegul Candir, in the parking lot of Bramalea Secondary School.

2006 is the Dawson College shooting. The next one to go past the 4+ is 2012, a security guard at University of Alberta Edmonton attempted a robbery, killing 3 colleagues and wounding a 4th, attacker arrested attempting to cross the us border. Then the 2016 La Loche shootings. 2024 in Toronto. And then the Tumbler Ridge shooting just the other day.
One instance in the 19th century, 43 in the entire 20th(as above, only 7 are above the 4+), and the first quarter of the 21st has 29 total with the listed 4. Tumbler Ridge is literally the highest casualty school shooting since 1884. As of the latest update on your linked page 35 victims, 8 dead 27 wounded excluding the attacker. Next closest is the École Polytechnique massacre in Montreal end of '89, 28 victims, 14 dead 14 wounded excluding attacker.

Thanks for linking that, I hadn't thought to look up a Canadian school shootings list. Gives more context to the history of it in Canada. I feel like it's important to note that the vast majority of Canadian school shootings have less than 5 total wounded and dead including the attacker, with many that have no wounded at all. A lot of them seem to be "crimes of passion" (jilted lovers, kids bullied until they snap, etc.) and seem to have a single intended victim, or kids being fucking stupid with a gun their parent/guardian was too stupid to properly secure...

Here's the list for US school shootings 2000-2025. 25 year total 642 school shootings. Including attacker(s) total dead 498, total wounded 953. Of those 642 instances.....only 16 count as mass shooting events, 4+ victims excluding attacker.

It was actually really interesting going through all this data. Upsetting, but interesting.