I had that impression, actually! I've noticed that SM primary in the USA is about .5 to 1 year ahead of standard USA curricula, but that the people I know who were educated internationally in high-math-achieving communities (including Singapore) tend to have been more like 2 years ahead. We used Star Publishing's Discovering Math secondary math series when homeschooling our children, and I realized that students on that syllabus were expected to complete most of univariate calculus by the end of the equivalent of tenth grade, which would put them about three years ahead of the typical US student, and two years ahead of an advanced US math student. And I've had friends from other countries who observed that the extent of math which high school math teachers are required to have taken for teacher certification was equivalent to what they had completed by tenth grade in their home country.
