https://en.wikipedia.org/wiki/List_of_attacks_related_to_secondary_schoolsWow. A Wikipedia list of school assaults and deaths, worldwide, since the 1850's. A very long list.
You can see a few things from this:
1) School assaults happen worldwide, and are not a problem isolated to the United States. Places like Germany, China, Russia, Malaysia, Austria, some of which surprised me.
2) These assaults are not limited to gun assaults, including knives, pipe bombs, molotov cocktails, and one interesting one, a flamethrower. Sometimes weapons found later, that the assailant did not use.
3) In every decade, there are more such incidents. And increasing worldwide, not just in the United States. Some of the increase might be because of wider reporting and shared information, but unquestionably increasing.
4) I'm surprised how often the chosen victims are teachers and not other students! Although in many cases, the teacher was targeted for attempting to stop the attack on someone else.
That's at least some barometer of whether these attacks are increasing, and what ratio of them are gun attacks. I notice in many cases the guns used are not the student's, but belonging to family members, and I don't know how you could legislate that away.
Another narrower list of "rampage killers", "that occurred at kindergartens, schools and universities, as well as their affiliated buildings":
https://en.wikipedia.org/wiki/List_of_rampage_killers_(school_massacres)
