I take a look just a couple minutes ago to the same UNESCO database and i've found there exist numbers of students enrolled by school level and country. So i will redo now the graph (let me one hour work 😅).

In that database i've found "ALMOST ALL" countries except a few pacific and caribbean "island-states" and the big (and strange) absence are Canada and Australia.

And yes, you're right, english is not my first language. I take note of your suggested title. Thanks a lot!