Jencks, page 139

I'll just quote this:

There is a popular theory among both educators and laymen that middle-class children work harder in school than poor children.  We cannot find any good evidence that this is so.  When we compare economically advantaged students to disadvantaged students with the same test scores, for example, we find that they get the same averages high school grades.  We assume that diligence has more effect on school grades than on standardized test scores, and we therefore conclude that economically disadvantaged students probably work as hard as economically advantaged students with comparable aptitudes.  More generally, we conclude that high school teachers reward a set of traits which, with the exception of academic aptitude, are not very class-related.  This clearly contradicts most people's preconceptions.  We suspect, though we certainly cannot prove, that these preconceptions are based on a misunderstanding of the dominant values of working-class families.  While a few lower-class and working-class children behave in ways that schools find unacceptable and try to punish, the great majority evidently do not.  The deviant minority seems, however, to shape middle-class stereotypes of working-class values and behavior.

My main thought from this is that the 60's and 70's seem to have been a better situation than I thought.  Why haven't we made more progress?