One of the biggest and most pressing educational problems confronting many countries around the world today is the inequality of school achievement. Although the problem has long been with us, in recent times, it has become far more transparent through the use of international measurements such as the Progress in International Reading Literacy Study (PIRLS), Trends in International Mathematics and Science Study (TIMMS), and especially OECD’s Programme for International Student Assessment (PISA). All three report their 3- or 5-year findings in ways which not only rank the performance of the participants from top to bottom, above and below a central standard (e.g., a score of 500) but also identify the range of scores within individual countries between the highest and lowest achievers. Some nations rank consistently well or poorly, while others rise and fall in the rankings; some countries have a very narrow range of scores between top and bottom students, while others have...