A clear explanation of the data and the method, so you can judge how much weight to give the numbers.
Every number here comes from the Delaware Department of Education’s open assessment data and its online school report card, for four high-school tests: the grade 11 SAT School Day (its Reading and Writing section and its Math section, 200-800), the DeSSA Biology test (300-900) and grade 11 DeSSA Social Studies (300-900). For each school, district and the state, and for each test and year, Delaware publishes:
Where Delaware’s own level counts exist, the bars are those counts. That is every 2026 test for the state, every SAT and Social Studies district, and most schools; and, through the all-grades view, most high schools’ SAT from 2023 and Biology from 2024, since at a high school that view holds just that one test’s students. The report card hides a count below 5; we fill it back in from the published number tested and number proficient when only one count in that half is hidden, and split the half’s known total by the fitted curve when both are. Districts and the state in 2023-2025 are then added up from those schools wherever at least half their students are covered.
Everything else is modeled from Delaware’s real average and proficiency rate: a normal curve whose mean is the real average, with its spread set so the share at Level 3 or above is the real proficiency rate. Checked against the 2026 real counts, the model lands within about 2.6 percentage points at every level for the state on the SAT, with a median worst-level gap of about 3.6 points for a district and 4.3 for a school. Biology and Social Studies scores are more lopsided than a normal curve, so their modeled bars are rougher (about 7 points at the state), which is why the real counts are used wherever Delaware prints them.
A percentile compares a score with that year’s Delaware public and charter school students who took the same test, by the school where they tested. The SAT and Social Studies count grade 11 students in the state’s spring School Day testing (about 9,700 in 2026); the few 10th and 12th graders who also took the School Day SAT are not included, and weekend SAT scores never are. Biology counts the students in grades 9-12 who took it (about 10,900 in 2026, two in three of them in grade 10). Delaware hides groups of fewer than 15 students.
Delaware publishes the exact score range for each level (e.g. for SAT Math, Level 3 is 530-640). Given a score, we:
That gives the percentile: the estimated share of students in the group who scored at or below the entered score.
The bell-like curve on each chart is a truncated-normal distribution centered on Delaware’s real average. Where the level counts are Delaware’s own, its spread is the one that best fits them. It’s there to visualize the shape of the group’s scores. The level counts set the headline percentile; the curve only decides where inside the student’s own level the line falls.
Each test has four levels; Level 3 and above is proficient.
The SAT levels are from Delaware’s SAT performance level tables, which print the same ranges in 2017 and in 2026. Biology and Social Studies are from Delaware’s DeSSA cut score charts; the Social Studies chart was approved by the State Board in November 2023. The score range for each level, by year, is on the score guides.
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 whole state.
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