Education and interest in politics

It is often claimed in popular debate that education is a "public good". This is generally invoked to justify public funding for education. What "public good" means exactly is usually undefined but there seems to be a general notion that higher levels of education somehow make people better citizens. For this reason economists and political scientists have looked at whether education makes people more likely to vote: it does.
One could also ask does education make people more interested in politics? The graph uses ESS data for Ireland to show a measure of interest in politics by education level completed. There is a correlation with those who have completed tertiary education being significantly more interested. Whether this is a causal link, of course, is a harder question.