How we estimate percentiles: Louisiana high school

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 the Louisiana Department of Education's public LEAP 2025 results, as published in its yearly achievement-level summary files on doe.louisiana.gov. They cover the LEAP 2025 high school tests: English I, English II, Algebra I, Geometry and US History from 2017-18, Biology from 2018-19 and Civics from 2024-25, for the school years ending in 2018, 2019 and 2021 through 2026 (there was no spring 2020 test). For each school, school system and the state, the files report:

the percentage of students at each of the five achievement levels (Unsatisfactory, Approaching Basic, Basic, Mastery and Advanced), as whole numbers. Louisiana does not publish how many students each group tested, so we work with the percentages themselves, and
from those percentages, an estimated average score: the center of the bell curve that best matches the share of students below each level’s cut score.

Louisiana also publishes the same results in a second file with student-group breakdowns. We checked the two against each other: from 2019 on they agree on every result. For 2018 the second file is a later revision that differs on 11 school and school system results by one to four points, so for those 11 we use the later revision.

Who is counted

These numbers are the students who took this end-of-course test during the school year, in the fall and spring testing windows together. Louisiana publishes each group's results as whole percentages, not counts. Middle-school students who take a high-school course test early (most often Algebra I or English I) are included, counted at their middle school.

Every student enrolled in a course with a LEAP 2025 test takes it, so a percentile compares a score with that year's takers of the same test, not with every student of the same age. Each test has roughly 38,000 to 53,000 takers statewide a year.

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

How the percentile is estimated

Louisiana publishes the exact scale-score range for each achievement level (e.g. on Algebra I, “Mastery” is 750-804). Given a score, we:

identify which achievement level the score falls in;
count everyone in the lower levels as scoring below;
within the score's own level, spread that level's students along the group's fitted curve (below) rather than evenly across the level's range. Students bunch up toward the middle of the scale, so an even spread would put too many of them out at the far ends of the lowest and highest levels.

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 achievement level matches the level percentages, centered on that estimated average score. It's there to visualize the shape of the group's scores. The level percentages set the headline percentile (steps above); the curve only decides where inside the student's own level the line falls.

When a group's students all sit in one or two levels, the percentages can't say how spread out their scores are, and the fitted curve can come out far too narrow. Those curves are drawn no narrower than one fifth of the statewide spread, which is about the size of the test's own measurement error, and inside the student's level the percentile spreads that level's students evenly instead.

About one school result in twenty-three gets a wide default curve for that reason, most of them Algebra I results at middle schools, where the students who take the course early nearly all reach Mastery or Advanced. About a dozen results have nearly every student at Unsatisfactory; their curve sits at the bottom of the scale.

Levels Louisiana hides

To protect privacy, Louisiana prints a level as “1 or less” when under 1.5% of the group is in it, and prints no levels at all for a group of fewer than 10 students (those results are left out). Because the five levels add up to 100, the hidden levels share whatever the printed levels leave over, which is never more than a few points. We give each hidden level that share one point at a time, starting with the level the rest of the group's results point to. The printed levels are kept exactly, apart from the one-point rounding differences that whole percentages always leave.

Why estimates are still useful: the achievement-level percentages are real for each group. The average score shown is estimated from how students split across the levels, 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, school system, 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.

Cut scores

Every LEAP 2025 high school test is scored from 650 to 850, with 750 the start of Mastery on every test. The other cut scores differ by test; the score range for each level is on the score guides. Each test's ranges are written into Louisiana's assessment rules (Bulletin 118), and each test has kept the same ranges since its first year: English I, English II, Algebra I, Geometry and US History since 2017-18, Biology since 2018-19 and Civics since 2024-25. The Department's current grade conversion tables print the same ranges.

The high-school progress report

The paid progress report puts every high-school test your child took in one table, with the percentile at each level from the school to the state, and charts each subject across the years.

Each course exam is its own point. Every Louisiana high-school test here is a course exam (such as Algebra I or English II), taken by the students in that course that year, a different group for each course, so the report does not join them with a line.
Earlier years are compared statewide only. You can add your child’s grades 3-8 LEAP scores in the same subjects. The tool doesn’t know which middle school or school system they attended, so those years are compared with every student in the state in that grade, not with this high school or its school system.
The report opens on the statewide view, the one level with a result for every test.

Limitations to keep in mind

Percentiles are estimates, not official rankings. Treat a "62nd percentile" as "roughly the top 40%," not an exact standing.
Five achievement levels are a coarse summary, and small schools have few students, so their estimates are noisier. Because Louisiana publishes whole percentages without counts, a small school's levels move in steps of several points per student.
Some charter schools are their own school system. Louisiana prints no separate school system result for most of them, since it would be the same students as the school.
The older four-level end-of-course tests that some graduating seniors and retesters took in 2017-18 and 2018-19 (US History, Biology and English III), and LEAP Connect, the alternate assessment, are not included.

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