A new study of mathematics curricula and classroom content in 40 countries reveals that while most eighth-grade teachers are focused on algebra and geometry, their U.S. counterparts are teaching simple fractions, ratios, percentages and other topics that come up in the sixth grade internationally. Researchers at Michigan State University and the University of Oklahoma compared 37,000 American eighth-grade math students and 1,900 math teachers across nine states and 13 school districts with their peers in other countries, showing that the U.S. is two years behind in terms of math rigor. The fault lies with the decentralized U.S. educational system, the authors say — 15,000 local school districts in 50 states, each exercising de facto control over its own curriculum.

Writing in last month’s issue of American Journal of Education, a research team headed by William Schmidt of Michigan State finds that family income is a heavier predictor of academic success in the U.S. than in most other countries. The higher the percentage of college-educated parents in an American school district, the tougher the math classes are likely to be. In other countries, all students get the same demanding curriculum.

“America’s schools are far from being the equalizers we, as a nation, want them to be,” Schmidt says. But help is on the way. A math curriculum from kindergarten through 12th grade, developed by Schmidt and adopted by more than 40 states, will be in the classroom next year, with algebra beginning in seventh grade.