This article examines how international differences in age-grade distributions and grade effects contribute to science scores among 27 Organization for Economic Cooperation and Development countries. As shown in the 2006 Program for International Student Assessment, countries vary substantially in the grade distribution of 15-year-olds. The costs…

Compared performance of high- and low-education adults on traditional and meaningful space and reasoning measures. Separate analyses of variance for reasoning and space revealed main effects for education and age on both abilities. Results indicated highly educated older people performed more like their younger peers. (Author/JAC)