How GreatSchools Ratings Are Calculated
GreatSchools, the most widely used school rating platform, produces 1–10 ratings based primarily on:
- Test score performance (weighted most heavily): How students score on state standardized tests vs. the state average
- Student progress/growth: How much students improve year over year (though this is weighted less)
- College readiness: For high schools — AP/IB course enrollment and pass rates, SAT/ACT participation
- Equity: How well the school serves students with different demographic backgrounds
Despite including growth and equity components, the ratings remain heavily influenced by raw test scores — which means they heavily reflect demographics.
The SES Correlation Problem
Here is the fundamental limitation of score-based school ratings: wealthy areas almost always have high-rated schools, not because of superior teaching, but because students from higher-income families arrive at school with more academic preparation, better nutrition and health, more stable home environments, and more educational enrichment outside of school.
Research from Stanford's CEPA (Center for Education Policy Analysis) found that differences in school test scores across districts are explained more by family income and demographics than by school quality. A school in an affluent suburb might rate 9/10 while delivering average instruction. A school in a lower-income urban area might rate 4/10 while doing exemplary work given its starting point.
Value-Added Models: A Better Measure
Educational researchers increasingly prefer value-added models (VAM) or student growth measures as better indicators of school effectiveness. These measure how much students improve compared to similar students elsewhere — controlling for where they started.
A school that takes students from the 20th percentile to the 45th percentile is doing more educationally than a school that takes students from the 80th to the 82nd percentile, even though the second school's scores are higher.
Many state report cards now include growth measures. Look for these alongside absolute performance metrics when evaluating schools.
State Accountability Systems Vary Widely
Under the Every Student Succeeds Act (ESSA), each state designs its own accountability system for rating schools. This means a 4-star school in Massachusetts is not comparable to a 4-star school in Mississippi — the states use different metrics, thresholds, and methodologies.
Always compare schools to their state benchmarks, not to absolute national standards.
What to Look for Beyond Ratings
Metrics that often reveal more about school quality than overall ratings:
- Chronic absenteeism rate: Students missing 10%+ of school days. High rates indicate poor school climate, health challenges, or disengagement. National average is ~15%; schools under 10% are doing well.
- Suspension and expulsion rate: Harsh discipline cultures correlate with worse outcomes. Zero-tolerance policies are falling out of favor for good reason.
- Arts and music program existence: Research links arts education to engagement and graduation rates. Budget cuts typically hit arts first.
- Counselor-to-student ratio: The ASCA recommends 1:250; many schools are at 1:400+. Fewer counselors means less individual support.
- Special ed support: Ask about IEP implementation quality, inclusion rates, and resource room availability.
Use MySchoolPeek to access verified NCES data on enrollment, staffing ratios, demographics, and free lunch rates for any US public school.