By using prefectural data of achievement tests in Japan, we investigate empirically which factors affect the achievement of elementary school pupils and junior high school students. In our regressions, we find that the ratio of grandparents living with their grandchildren has a strong positive effect on achievement. Family income and the ratio of people having completed university, which is a proxy of the education level of parents, affect achievement positively. The quality of teachers, but not the quantity, is important for achievement. Public education expenditure does not contribute at all.