Orange Unified

Step 1 · Each year's result

For each grade tested, take the average (mean) scale score from the California Department of Education's results file, and subtract the lowest score that counts as "Standard Met" for that grade. That is the grade's distance from standard. Weight each grade by its share of the students tested, then add the grades up. Grades where the state hides the average because ten or fewer students tested are left out entirely.

Step 2 · The average and the normal range

1. Average: add the yearly results and divide by how many there are. −34, −26, −25, −23, −19, −31, −35, −26, −18, −17, −13 → −24.3
2. Typical year-to-year change: how far the result moved from each year to the next, ignoring up or down. 2015→2016: 8 · 2016→2017: 1 · 2017→2018: 2 · 2018→2019: 4 · 2019→2021: 12 · 2021→2022: 4 · 2022→2023: 9 · 2023→2024: 8 · 2024→2025: 1 · 2025→2026: 4 → average 5.3
3. Normal range: multiply the typical change by 2.66, then add it to the average and subtract it. 5.3 × 2.66 = 14.1. Upper limit −10.2, lower limit −38.4.

Why 2.66? It is the standard factor from quality control, the work of Walter Shewhart and W. Edwards Deming. It turns "how much the result typically changes in a year" into "how far it can wander by chance alone".

Years with no result (no state tests were given in spring 2020) are skipped: the year-to-year change runs from the last year with a result to the next one.

Step 3 · Free or reduced-price meals

The share of enrolled students eligible for free or reduced-price meals — for a district, the total across its schools. From 2014–15, 2015–16, 2016–17, 2017–18, 2018–19, 2020–21, 2021–22, 2022–23, 2023–24, 2024–25, 2025–26.