Complex sentence: Some believe that the difference in scores is because of the overall gap in American society between blacks and whites students in education.This gap is caused from the nature of the nation; black students tend to go to schools that are less financially well off.
Split into simpler sentences: Some believe that the difference in scores is because of the overall gap in American society between blacks and whites students in education. Some studies suggest that this is caused by the fact that black students tend to go to schools that are less financially well off.