In an article on the Freakonomics Blog, Stephen Dubner overviews a paper written by a Notre Dame economist on the relation between religion and education. For an additional year of education, it was found that the effect on religious participation was

a decrease of 4%. The findings of this study can certainly be questioned, though. Does education cause a decrease in religious participation or is there simply a correlation there that can be explained by one or more other factors? Answering this question is difficult to say the least, but the study is interesting regardless of the answer.

Source: Freakonomics Blog