"Probably"? Of course it has to do with both, and it's practically impossible to say what it has more to do with objectively. If the immigrants were exactly li

"Probably"? Of course it has to do with both, and it's practically impossible to say what it has more to do with objectively. If the immigrants were exactly like the natives, their school results would be exactly the same as well. Or, if the school was perfectly adapted to the immigrants, they would score the best in the world. In reality, you can look more into how to keep "undesirable" people out of your country (and deport the disadvantaged people who lower the average scores?), or you can look more into how to develop the school system so that even the disadvantaged people get a good education out of it. Finland chooses the latter, more constructive, more humane, more equal, and as far as we believe the PISA and similar studies, more efficient stance. Ethics aside, you're free to choose otherwise.