How we estimate percentiles

A clear explanation of the data and the method, so you can judge how much weight to give the numbers.

What the data is

Every number here comes from official public test-results files: the Virginia Department of Education assessment data (SOL, ELA & Math, grades 3-8). These files report, for each school / grade / year:

the percentage of students in each performance level (school rows) or the real count (district/state rows), plus the number tested, and
from those figures, a mean we estimate from the count-weighted midpoint of each performance level’s scale range, which we then fit a curve around.

Important: the public data does not contain individual student scores, only these group summaries. So no tool can compute a true rank of one child against every other child. What we provide is a well-grounded estimate.

How the percentile is estimated

Virginia publishes the exact scale-score range for each performance level (e.g. on every SOL test, “Pass/Proficient” is 400-499). Given your child's score, we:

identify which performance level the score falls in;
count everyone in the lower levels as scoring below;
within the score's own level, use linear interpolation across that level's count, assuming scores are spread evenly across the level's range.

That gives the percentile: the estimated share of students in the group who scored at or below the entered score.

About the smooth curve

The bell-like curve on each chart is a truncated-normal distribution fitted so that its area within each performance level matches the level counts, anchored to a mean estimated from the count-weighted midpoint of each level. It's there to visualize the shape of the group's scores. The headline percentile comes from the counts (step above), not from the curve.

Why estimates are still useful: the performance-level counts are real and complete for each group. The mean figure shown is approximated from where students fall within each level, and, as with every state, the only other assumption is how scores are distributed inside a level, a small and bounded range. Across a whole school, district, county, or the state, that assumption averages out well, so the comparison ("above/below average here vs. statewide") is reliable even though the exact percentile is approximate.

Limitations to keep in mind

Percentiles are estimates, not official rankings. Treat a "62nd percentile" as "roughly the top 40%," not an exact standing.
Small schools have small counts, so their estimates are noisier.
Some school/grade cells are suppressed by the state (for privacy, small groups) and won't appear.
Every Virginia SOL (Standards of Learning) test is reported on a common 0 to 600 scaled score with the same cut points for every grade and subject: a score of 400 is the pass line (Pass/Proficient) and 500 is the advanced line (Pass/Advanced), so the three public levels are Did Not Pass (0-399), Pass/Proficient (400-499), and Pass/Advanced (500-600). Virginia publishes the percentage of students in each band plus the number tested for every school, division, and the state, so each group's curve is fit from those bands anchored at the 400 and 500 cuts. Reading and math cover grades 3-8 and science covers grades 5 and 8, for spring 2023, 2024, and 2025 (the years the state's public download tool serves). Virginia is compared at the school, division, and state levels (a division is the county or city school system; there is no separate county tier). For grade 3-8 reading and math the state's two failing sub-levels (Basic and Below Basic) are combined into a single Did Not Pass band in all public data, matching the wording on the family score report.
Charter schools appear as their own districts in the state files and are included in the school, district, county and statewide comparisons.

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