This paper explores the PISA [Programme for International Student Assessment] achievement of twenty countries in light of some of their demographic differences. SES [student socioeconomic status], nuclear family, gender, home language, and native status were predictive of achievement for every country. Demographics accounted for as little as 8 percent to as much as 22 percent of individual score variance depending on the country and subject. Being male was almost a universal advantage in math, but was a far greater disadvantage in reading for every country. The relative performance of some countries changed when scores were adjusted for demographic differences; however, the Asian countries and Finland remained on top. Instructional strategies related to countries performing above expectations were explored.