For school-aged children from marginalized groups, cultural differences including language, ethnicity, class, and religion increase the distance between their cultural historical worlds and the cultural historical world of mainstream instruction and assessment. In the USA, studies of mathematics and science teaching suggest that these students are doubly disadvantaged. Stigler and Hiebert's (1999) book, The Teaching Gap, compared Trends in International Mathematics and Science Study (TIMSS) performance of US mathematics and science students to students in 40 nations and analyzed videotapes of classroom mathematics instruction in the USA, Japan, and Germany. Findings of significant differences in teaching across cultures but small differences within cultures led them to conclude that teaching is a cultural activity and that, despite US teachers agreeing with reform efforts, there was little evidence of change. They concluded: "Our students are (sic) being shortchanged. They could be learning much more and much more deeply than they are now" (p. 5).