Methodology
How we collect, process, and present education data for every US county.
Data Sources
SchoolsByCounty draws on two primary federal data sources, both freely available to the public:
National Center for Education Statistics (NCES)
The NCES Common Core of Data (CCD) provides school-level and district-level data for every public school in the United States. We use the following datasets:
- School District Finance Survey (F-33) — per-pupil expenditure by district
- Public School Universe — enrollment counts, school type, grade span
- Local Education Agency Universe — district-level demographics and finance
- Adjusted Cohort Graduation Rate (ACGR) — four-year graduation rates
Source: nces.ed.gov/ccd
U.S. Census Bureau — American Community Survey (ACS)
The ACS 5-Year Estimates (2019-2023) provide county-level demographic and socioeconomic data. We use the following variables:
- Educational attainment — percentage of adults 25+ with a bachelor's degree or higher
- School enrollment — enrollment by level (elementary, secondary, college)
- Median household income — used for contextual comparisons
Source: data.census.gov
Key Metrics
Each county page presents the following education metrics:
| Metric | Source | Description |
|---|---|---|
| Per-Pupil Expenditure | NCES F-33 | Total current spending divided by student enrollment in the county's school districts |
| Graduation Rate | NCES ACGR | Four-year adjusted cohort graduation rate for public high schools |
| Student-Teacher Ratio | NCES CCD | Total enrollment divided by full-time equivalent teachers across districts |
| Bachelor's Degree Rate | Census ACS | Percentage of adults aged 25+ holding a bachelor's degree or higher |
| School Score | Composite | 0-100 percentile-rank score combining the above metrics (see Scoring section) |
School Score Calculation
Each county receives a School Score from 0 to 100 using percentile-rank methodology. The process works as follows:
- Data aggregation: Individual school and district data is aggregated to the county level. Per-pupil expenditure is enrollment-weighted across districts. Graduation rates are averaged across high school districts in the county.
- Percentile ranking: Each county is ranked against all 3,143 US counties on each metric. The percentile position determines the score: a county at the 75th percentile for graduation rate scores 75 on that dimension.
- Composite scoring: The individual metric percentiles are combined into a weighted composite. Graduation rate and per-pupil expenditure receive the highest weights, reflecting their strong correlation with educational outcomes.
- Normalization: The final composite is normalized to a 0-100 scale where 100 represents the best-performing county and 0 the lowest. A score of 50 represents the national median.
Counties with incomplete data (e.g., missing graduation rate or expenditure data) receive adjusted scores based on available metrics. These counties are flagged on their individual pages.
Data Freshness and Update Schedule
Government education data follows an annual release cycle. Our current data reflects:
- NCES data: School year 2022-2023 (the most recent complete release from the Common Core of Data)
- Census ACS data: 2019-2023 5-Year Estimates (released December 2024)
We update our dataset within 30 days of new NCES or Census data releases, typically once per year. The “Data vintage” label on each county page indicates which release is currently reflected.
AI-Generated Content Disclosure
SchoolsByCounty uses artificial intelligence to generate narrative descriptions on state summary pages. These narratives are produced by the Claude AI model (Anthropic) using structured government data as input. The AI does not fabricate data points — all statistics referenced in narratives come directly from the underlying NCES and Census datasets.
Specifically, AI-generated content appears in:
- State-level education narrative summaries
- County comparison text on state pages
- Contextual descriptions of education trends
All data tables, charts, scores, and rankings are computed directly from government source data without AI involvement. Human editors review AI-generated narratives for accuracy before publication.
Limitations
- NCES data covers public schools only. Private school enrollment and performance are not included in county scores.
- Per-pupil expenditure reflects total current spending and may include costs (e.g., transportation, facilities) that vary widely by geography.
- Graduation rates are adjusted cohort rates for public high schools. Alternative education programs and GED completion are not counted.
- County boundaries do not always align with school district boundaries. Where districts span multiple counties, data is apportioned by enrollment share.
- Education quality is multidimensional. The School Score captures measurable outcomes and inputs but cannot reflect teacher quality, curriculum rigor, extracurricular offerings, or school culture.
Questions or Corrections
If you believe any data on this site is inaccurate or have questions about our methodology, please contact us. We take data accuracy seriously and will investigate all reported discrepancies.