I live in a very segregated county that is divided between the low-income urban area that is made up almost entirely of minorities and immigrants and the high-income suburban area which is mostly white and made up of non-immigrants. Hands down, the immigrant group seems to be the most hardworking and serious about school. Non-immigrants (from both sides of the county) tend to slack a whole lot more and tend to expect good grades to be handed to them just for showing up. The suburban (high-income) kids tend to have a much better foundation than the urban (low-income) kids, but that's to be expected, given that the quality of public schools in the suburbs are light-years better than in the city.