One other thing that i have noticed, is that in "rich" countries, knowledge of trivial and basic stuff are celebrated in the name of "positive reinforcement". This gives students the false idea that they have "mastered" something while they have just started learning. IMO, this is extremely harmful to the student's psychology.
They have the basics, motivation, and opportunities.
Those that stay in poor countries don't have opportunities nor motivation. Those that come from rich countries don't have the basics nor motivation.
It's a generalization, of course.