While academic achievement western societies still isn't as much determined by individual skill as many people would like to believe, it's worse in the countries the immigrants come from, and additional factors like language barriers and discrimination (intentional, structural or even accidental) render the idea of inheritability quite useless.
Another problem is that studies have identified environmental factors which influence intelligence much more than any known individual genetic factors. For example infections with Malaria or other parasites, but also the duration and quality of school attendance.
You will notice that none of the "twins raised apart" studies include such factors, because virtually no children in western societies have these problems.
And that's why the impact of the education system and socioeconomic factors on academic achievement are vastly underestimated, especially because people keep bringing up these inheritability studies.