Among the 8 OECD countries that have between 15% and 30% of students with an immigrant background, which includes the United States, four show a smaller performance gap for immigrants on PISA while three show a larger performance gap for immigrants than the United States (Figure 11.4.3 in PISA 2009 Results, Volume II). These differences need to be taken into account when interpreting differences in student performance. At the same time, the future economic and social prospects of both individuals and countries depends on the results they actually achieve, not on the performance they might have achieved under different social and economic conditions. That is why the results that are actually achieved by students, schools and countries are the focus of the subsequent analysis in this chapter.