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 Oklahoma State Department of Education assessment data (OSTP — English language arts and math in grades 3-8, and science in grades 5 and 8). These files report, for each school / grade / year:

the percentage of students in each of the four performance levels — for every school, district, and the state alike. Oklahoma does not publish student counts or the number tested, so these percentages are the only figures available; and
from those percentages, a mean we estimate by fitting a normal distribution across the official scale-score range for each performance level.

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

Oklahoma publishes the exact scale-score range for each performance level (e.g. for Grade 3 Math, Proficient is 300-320 and Advanced is 321-399). 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, 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.
The Oklahoma School Testing Program (OSTP) reports each grade and subject on a common 200 to 399 scale, across four performance levels: Below Basic, Basic, Proficient, and Advanced, with the Proficient line fixed at a scale score of 300 in every grade, subject, and year. Oklahoma publishes the percentage of students at each level for every school and grade rather than student counts, so figures are shown as percentages and the curve's center is estimated by fitting a normal distribution to those percentages across the official score ranges. Science is given in grades 5 and 8. No test was given in 2020 or 2021 (COVID). The 2024 scores were reported on a re-linked scale that the state later rescinded and restored to the 2017 to 2023 standard for 2025, so 2024 scale scores are not directly comparable to other years, though percentiles remain comparable. Oklahoma is compared at the school, district, and state levels (it has no separate county tier).
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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