Which is an absolutely deceptive way to look at the issue. First of all, they start counting in 2009. Guess what happens shortly after that? The only mass shooting in Norway ever. All of a sudden Norway is beating the USA.
That's a terrible way to see if a country has a school shooting problem. The source of your claim is "crimeresearch.org" which is an incredibly unreliable source, they even included into mass shootings things that were not mass shootings, such as a suicide bomber. Bogus source.
Fact is that the USA holds less than 5% of the world's population but accounts for 31% of global mass shootings.
Think about that for a second. School shootings are almost completely an American phenomenon.