Average IQ By State

If you grew up in Mississippi and moved to Massachusetts as a child, your IQ score would almost certainly go up, not because you became smarter, but because you would be attending better-funded schools that produce higher standardized test results. That is the single most important thing to understand about this ranking.

The entire spread from top to bottom is just 10.1 points: Massachusetts leads at 104.3 and Mississippi anchors the bottom at 94.2. For context, the standard error on most IQ tests is 3 to 5 points, which means a single person can score differently on the same test taken on different days. Much of the state-to-state gap falls within that margin of noise.

A 2018 review by Stuart Ritchie and Elliot Tucker-Drob, covering more than 600,000 people across multiple countries, found that each additional year of schooling raises a person's measured IQ by 1 to 5 points. Education does not just correlate with IQ. It moves the needle directly. That means the gap between first and last place is roughly equal to the effect of one to two extra years of school.

The obvious assumption is that states spending more on education should have higher IQ scores. That is partly true, but the data tells a more interesting story.

The link between per-pupil K-12 spending and average IQ is only moderate. South Dakota scores 102.8 on the IQ index despite spending just $13,600 per student, one of the lowest figures in the country. Meanwhile, New York spends $33,400 per student, by far the most in the nation, but its IQ estimate is only 100.7.

What tracks much more closely with IQ is whether students actually complete high school. States with higher graduation rates almost always have higher average IQ scores. The pattern holds across every region.

Massachusetts anchors the top of both indices: highest IQ (104.3) and first place in all four 2024 NAEP assessment categories. The state spends roughly $24,400 per student, about $5,400 above the national average. But spending alone does not explain its dominance. States like New Hampshire (104.2) and North Dakota (103.8) achieve similar IQ scores while spending significantly less.

The most encouraging example in the data is Mississippi. In 2013, the state ranked dead last nationally in K-12 achievement. It adopted comprehensive science-of-reading reforms, restructured school accountability, and by 2023 had climbed to 35th. When researchers adjusted NAEP scores for student demographics, Mississippi ranked first in the country in 4th-grade reading and math. Its IQ estimate, frozen in 2006, does not capture any of that progress.

California has the largest economy in the country, world-class universities, and tech companies that recruit talent globally. It also ranks 49th in this IQ index with a score of 95.5. At first glance, that seems absurd.

The explanation is not cognitive. It is linguistic. California has more than one million English Learner students, about 17.4% of its K-12 enrollment. Those students take the same standardized tests used to generate these IQ estimates, and only 10.3% of them meet English Language Arts proficiency standards, compared to 51.5% of native English speakers.

That gap closes fast. Data from California's Department of Education shows that once English Learners are reclassified as fluent, they match or slightly outperform native speakers on the same assessments. The testing gap is a language gap, not an ability gap.

Texas (100.0) and New York (100.7) show the same pattern at smaller scales. Both are high-immigration gateway states where large ESL populations pull down aggregate test scores. Nevada (96.5) and Arizona (97.4) complete the cluster. All four are statistically significant outliers on high school completion rate — not because their schools are failing, but because their student populations include millions of people still learning the language the tests are written in.

The numbers in this ranking were not collected by knocking on doors and administering IQ tests. They come from a 2006 study by Michael McDaniel at Virginia Commonwealth University, published in the journal Intelligence. McDaniel took NAEP reading and math scores from public school 4th and 8th graders, supplemented them with ACT and SAT composites, and converted the results into estimated IQ equivalents.

That approach has real blind spots. The NAEP only tests public school students, which means every kid in private school, parochial school, or homeschool is excluded from the data entirely. In states where those populations are large, the IQ estimate is built on an incomplete picture. McDaniel acknowledged this, noting a "downward bias" in states with high non-public enrollment.

More fundamentally, a standardized test measures what a student has been taught, not what they are capable of learning. A child who went through well-funded schools in a wealthy suburb and a child who attended underfunded schools in a high-poverty district are taking the same test from very different starting lines. The resulting IQ estimates capture the combined effect of school quality, household income, nutrition, and language background, not raw intelligence.

None of that makes the data meaningless. The patterns are real and consistent: states that invest in education, graduate more students, and have smaller ESL populations consistently score higher. But a ranking titled "Average IQ by State" is more honestly read as a ranking of educational infrastructure and childhood opportunity. The 10-point gap between Massachusetts and Mississippi reflects decades of divergent policy choices, not some fixed difference in the people who live there.