Material Deprivation

Material deprivation (by which we mean the extent to which people have or are denied certain material things in life - which includes things like your level of income, standard of housing, access to consumer goods and so forth) is frequently cited as one of - if not the - main cause of differential educational achievement.
Although the theory has gone in and out of political (and sociological) fashion over the past 50 or so years, most of the research in this area does suggest that there is some form of relationship between material deprivation (and it's mirror concept, material affluence) and educational success or failure.
For example, with the development of School League Tables in Britain in the 1990's, two very important points flow from their publication:
Firstly, the high proportion of students from affluent home and private school backgrounds who achieve high levels of success at GCSE and A-level.
Secondly, the fact that the students who, overall, achieve the least in our education system are over-represented in poor inner city and rural areas.
Thus, the above would suggest a strong correlation (at least) between material deprivation / affluence and educational achievement, with students from materially-advantaged backgrounds achieving high rates of success and students from highly-deprived regional and family backgrounds achieving the least.
We can, for example, see this idea in action when we think about pre-World War 2 Britain. In this society, with it's wide disparities of wealth and income, poverty and deprivation were obvious explanations for educational differences in achievement between upper / middle class children and their working class peers.
However, in the years following the 2nd World War 2, material conditions generally improved for the working classes (with the introduction of the Welfare State, National Health Service and 1944 Education Act that provided free, compulsory, schooling), their relative level of achievement (compared, that is, with other social classes) did not improve significantly. This "educational discrepancy" was not only clear in the 1950's, but was also manifest in the more generally-affluent 1960's.
This, in part, led the Plowden Report ("Children and Their Primary Schools", 1967) to conclude that only in extreme cases did poverty play a significant part in explaining differential educational achievement.