It doesn't take a mathemetician, biologist, or racist to understand that you're talking out of your daughter's dirty diaper.

Who is included in China's baseline aggregate?China’s baseline aggregate in the PISA dataset does not encompass the entire nation. Instead, it strictly comprises four highly developed, high-performing educational hubs in eastern mainland China, collectively referred to by the OECD as B-S-J-Z (Beijing, Shanghai, Jiangsu, and Zhejiang).

Context of the Sample--Because these four specific territories combined represent an urbanized and economically privileged population of roughly 180 million people, education policy researchers frequently point out that the sample is heavily selective. It excludes China’s massive rural populations and less-developed interior provinces, which means the baseline reflects China's absolute top-tier educational regions rather than a true national average.(Note: While other regions like Guangdong participated in an intermediate 2015 trial, the standardized baseline used for international ranking comparisons across the 2018 and latest 2025 testing cycles is entirely anchored to these specific four B-S-J-Z regions).

OK so the comparison of four of China's highest performing educational hubs to all of the USA population of same age student is statistically invalid then, correct?

Yes, from a strict statistical standpoint, direct head-to-head comparisons are invalid.In statistics, for a comparative analysis to hold integrity, the selected samples must be equivalent in their composition. Comparing a national, universally representative sample (the United States) to a highly selective, regional sample (the BSJZ regions of China) violates the fundamental rules of data sampling.Education policy researchers, psychometricians, and statisticians have heavily criticized this imbalance. The comparison fails statistical validity for several reasons:

1. Selection Bias and Wealth DisparitiesThe United States sample includes students from every demographic, geographic, and socioeconomic layer—from affluent suburban districts to underfunded inner-city and rural schools. Conversely, the BSJZ sample isolates a hyper-prosperous urban territory of roughly 180 million people. Shanghai and Beijing boast per-capita GDPs and educational funding levels that rival wealthy nations, meaning the data measures China's absolute educational elite, not its average.2. The Exclusion of Migrant Populations (Hukou System)Independent reviews, including a prominent study by the American Enterprise Institute (AEI), highlight a structural flaw known as the Hukou effect. In major economic hubs like Shanghai, children of internal migrant workers often face legal barriers to attending local public high schools. Because PISA tests 15-year-olds (who are entering high school), a vast population of lower socioeconomic background students are systematically excluded from the test sample because they are sent back to rural provinces.3. What the Real Picture Looks LikeWhen researchers attempt to measure China as a whole, the results look entirely different:The Rural Gap: Academic reviews of China's broader K-12 population note that internal testing in China's vast rural provinces shows scores that lag significantly behind international averages.National Projections: Researchers estimating a true, comprehensive national average for China suggest its actual performance would fall closer to the middle of the pack—comparable to countries like Turkey—placing a true Chinese national average below the US average in several categories.How the Data Should Be ReadThe OECD, which administers PISA, labels the entity "B-S-J-Z (China)" rather than "China" to acknowledge this limitation. The only statistically valid takeaway from the data is a comparison of peer environments: The US educational system's elite tiers (such as high-scoring sub-populations or top-tier suburban districts) compared to China's elite tiers.

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Replying to wzambon

And oh, yeah - math is racist.

Math is not racist.

Any more that biology is racist.

But the way they are taught can be.