"Nothing I have seen published using OLS, MLA, or any other technique suggests to me that the predictive power of pupil SES is identical in all countries. It differs by subject matter of the dependent variable. It differs by level of educational institution - primary, secondary, higher. It differs within different ethnic groups. It differs by school availability. And it differs by school quality. No academic debate, or any new piece of computer software, can negate what is perfectly obvious to every minister of education in every developing country, including Zimbabwe - that even parents of low socioeconomic status want more education for their children and will sacrifice a great deal to keep their children in school. While we may argue over the relative importance of one effect versus another, such arguments are irrelevant in the world of policy, where the only relevant questions are how to raise the availability of school quality inputs and how to distribute them more fairly. No one seriously argue that they should not be raised because academic achievement is conditioned by the home." - Stephen P. Heyneman, Multilevel Methods for Analyzing School Effects in Developing Countries, November 1989, Comparative Education Review :O I think I'm starting to understand why I do what I do now...