Leadership is the #1 most important factor. Bad leadership is seen immediately and it's consequences last for atleast 1 decade. I know a caribbean country where the education minister thought it would be a good idea to have all kids pass their exam to go to secondary school long story short that place now enjoys a crime wave over 400% more than before. Are these connected maybe, certainly difficult to prove but what happens when you put a kid that ain't too bright in a school they didn't pass for?
THEY FAIL. Before these kids would be put in special schools where they would be educated in manual jobs and they would excell and become middle class. She(the minister) fucked them up. And she did it for cheap political points. And I'm sure there are all kinds of examples from all over the world.