Parents anchor on the GreatSchools 1-10 number because it's the number a realtor will quote and the number Zillow will display. It is also one of the most misunderstood numbers in real estate. Here's what it actually measures, what it misses, and how to read it without making the classic mistakes.
What the headline score actually measures
GreatSchools' summary rating is a weighted blend of: test score performance (the biggest component), student progress over time, academic progress for low-income students, college readiness measures (for high schools), and an equity subscore comparing outcomes across demographic groups.
The dominant factor for the headline number is raw test scores, which correlate heavily with the income of the families who enroll. A 9/10 school in a wealthy suburb may add less educational value than a 5/10 school in a working-class neighborhood — they're measuring inputs as much as quality.
The subscore that matters more
Look at the 'Student Progress' subscore (sometimes called 'Academic Progress' or 'Growth'). This measures how much students improve year-over-year, controlling for where they started. It's the closest thing to a measure of what the school is actually adding.
What the rating doesn't capture
- Teacher tenure and turnover — high turnover is a strong negative signal
- Class sizes — especially in K-3, this matters more than test scores
- Special education quality — varies wildly within the same district
- Counseling and mental health resources — increasingly important
- After-school programs, arts, and athletics depth
- Culture and discipline philosophy — only visible by walking in
How to actually evaluate a school
- 01Pull the state report card — it has more granular data than GreatSchools
- 02Look up teacher turnover on the district's HR page or via a public records request
- 03Visit during a regular weekday — many schools allow scheduled tours
- 04Talk to 2-3 parents whose kids actually attend, not parents promoting the school
- 05Read the most recent school board minutes — they reveal real issues
- 06Check if the school has a waitlist; if yes, demand is a meaningful signal
Red flags to watch for
- Principal turnover more than once in three years
- Teacher turnover above 20% annually
- Sudden drop in test scores year-over-year
- Heavy reliance on substitute teachers in core subjects
- Active lawsuits over special education compliance
Questions readers ask
Q01Is private school worth it?
For most kids in a good public district, no. For specific situations — special needs that aren't well-served, religious instruction, a child who's a poor fit for a large public — yes.
Q02How much should school quality drive my city choice?
If you have school-age kids, a lot. Switching districts mid-elementary or mid-middle school is meaningfully disruptive; pick the city with the right district from the start.
Q03Do test scores really matter for college admission?
Less than they did. Most selective colleges are test-optional now. The bigger factor is the rigor of the high school's curriculum — does it offer enough AP/IB courses to demonstrate challenge?
