How we estimate percentiles: Indiana 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 official public test-results files: the Indiana Department of Education data center, for the two high-school tests Indiana gives every year: the SAT, taken at school by juniors (its Reading and Writing and its Math sections, 2022 to 2026), and the ILEARN Biology end-of-course test (2019 and 2021 to 2026). These files report, for each school, school corporation and the state, and for each test and year:

• the real number of students in each performance level and the number tested. We use those counts exactly as Indiana printed them. County results add up the school corporations in that county (and, for a corporation that spans several counties, its schools), and
• from those counts, an estimated average score: the center of the bell curve that best matches the share of students below each level’s cut score.

Who is counted

Biology includes every student who took the ILEARN Biology end-of-course test that school year, in any grade: middle-school students who take Biology early are included, counted at their middle school. In 2019 Indiana counted only students enrolled for at least 162 days of the school year. From 2025, students using an Education Scholarship Account are not in the school and school-corporation numbers. The SAT tests include the juniors who took the SAT at school in Indiana’s March SAT School Day; weekend SAT scores are not included.

Biology is a course test, taken by whoever is in the course that year, so a percentile compares a score with that year’s Biology takers (about 85,000 students in 2026, around 4,000 of them at middle schools), not with every student of the same age. The SAT is taken by the whole junior class (about 81,000 students in 2026), so an SAT percentile compares a score with Indiana juniors who took it at school that spring. It is not the same as the national percentile on a College Board score report, which compares with test takers across the country.

The statewide row is Indiana’s own statewide total, and it includes students at non-public schools that take the state tests. In 2019 the school and corporation rows count only students enrolled at that school or corporation for the 162 days, so they add up to a little less than the statewide row (about 95%).

How the percentile is estimated

Indiana publishes the exact scale-score range for each performance level (e.g. for SAT Math, “Approaching College-Ready Benchmark” is 460-520, and for Biology from 2024, “At Proficiency” is 561-572). Given a score, we:

1. identify which performance level the score falls in;
2. count everyone in the lower levels as scoring below;
3. 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. Checked against published statewide score distributions, this lands within about one percentile point of the true value for a typical score.

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, centered on that estimated average score. It's there to visualize the shape of the group's scores. The level counts 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 counts can't say how spread out their scores are. A curve that comes out too narrow is drawn no narrower than one fifth of the statewide spread, and inside the student's level the percentile spreads that level's students evenly instead. About one school result in fifteen here (most often SAT Math at schools where nearly every student is below the benchmark) gets a wide default curve instead, which places a score inside its level close to an even spread.

The SAT has only three levels, so its curve rests on two cut scores, and the Reading and Writing “Approaching” band is narrow (450-470). For a small school that makes the curve’s width less certain than for Biology, which has four levels; the counts in each level are still exact.

Cut scores

The SAT reports each section on a 200-800 scale, in steps of 10. Indiana sets its own three levels on it: Below, Approaching and At College-Ready Benchmark. For Math they are 200-450, 460-520 and 530-800; for Reading and Writing, 200-440, 450-470 and 480-800. The “At” level starts at College Board’s own college-readiness benchmark (530 and 480). Indiana educators set the Approaching level after the first SAT School Day in spring 2022, and the same table applies through 2026, including the digital SAT used from 2024. It comes from IDOE’s “SAT School Day Performance Cut Scores” document, linked from its high-school assessment page.

ILEARN Biology has four levels: Below, Approaching, At and Above Proficiency, with At Proficiency marking the state proficiency line. Indiana moved Biology to a new scale and new cut scores starting with the fall 2023 test, after new science standards. So 2019 to 2023 use the original 7350-7650 scale, and 2024 to 2026 use the new 500-620 scale, with At Proficiency from 561. Scale scores from the two periods don’t line up; percentiles do. Both tables come from IDOE’s ILEARN cut-score documents (the 2019 edition and the August 2024 and August 2026 editions). The score range for each level, by year, is on the score guides.

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.

• Lines join only the same kind of comparison. A grade-level test is taken by every student in that grade, so one subject’s grade-level results form a line across the years; the SAT is Indiana’s grade 11 test. A course exam (Biology) is taken by the students in that course that year, a different group each year, so it is its own point.
• Earlier years are compared statewide only. You can add your child’s grades 3-8 scores in the same subjects. The tool doesn’t know which middle school or school corporation they attended, so those years are compared with every student in the state in that grade, not with this high school or its corporation.
• 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.
• Small schools have small counts, so their estimates are noisier.
• Indiana hides the results of any group with fewer than 10 students, to protect their privacy, and those schools won’t appear (about one school result in ten, and no more than about half of one percent of a year’s students). The school-corporation, county and state results still count those students. The 2024 SAT files hid nothing, so that year small schools appear too.
• Not included: 2020 (no test, COVID); the ISTEP+ grade 10 test (2018, 2019 and 2021, whose files show only how many students passed); the optional ILEARN U.S. Government test; and I AM, Indiana’s alternate test.
• Indiana is compared at the school, school corporation, county and state levels. Non-public schools that take the state tests appear as schools, with county and state comparisons but no corporation.

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