Costano Elementary: math

The shaded band is this school's normal range. If nothing about how it works changes, nearly every future year should land inside it. Zero means the typical student just meets the state standard. The small numbers under the years are how many students were tested.

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.

2015 from sb_ca2015_1_csv_v3.zip

Grade	Line in file	Average score	Standard Met	Distance	Students	Weighted
3	83,367	2354.1	− 2436	−81.9	× 68 / 356	−15.6
4	83,368	2398.5	− 2485	−86.5	× 55 / 356	−13.4
5	83,371	2409.3	− 2528	−118.7	× 61 / 356	−20.3
6	83,372	2445.8	− 2552	−106.2	× 59 / 356	−17.6
7	83,375	2469.7	− 2567	−97.3	× 53 / 356	−14.5
8	83,376	2506.6	− 2586	−79.4	× 60 / 356	−13.4
Sum, rounded to a whole point						−95

2016 from sb_ca2016_1_csv_v3.zip

Grade	Line in file	Average score	Standard Met	Distance	Students	Weighted
3	77,299	2376.7	− 2436	−59.3	× 67 / 353	−11.3
4	77,300	2378.1	− 2485	−106.9	× 61 / 353	−18.5
5	77,302	2398.3	− 2528	−129.7	× 58 / 353	−21.3
6	77,304	2425.6	− 2552	−126.4	× 55 / 353	−19.7
7	77,307	2443.9	− 2567	−123.1	× 58 / 353	−20.2
8	77,308	2498.1	− 2586	−87.9	× 54 / 353	−13.4
Sum, rounded to a whole point						−104

2017 from sb_ca2017_1_csv_v2.zip

Grade	Line in file	Average score	Standard Met	Distance	Students	Weighted
3	79,434	2372.6	− 2436	−63.4	× 52 / 350	−9.4
4	79,435	2373.6	− 2485	−111.4	× 61 / 350	−19.4
5	79,438	2385.4	− 2528	−142.6	× 61 / 350	−24.9
6	79,440	2409.1	− 2552	−142.9	× 60 / 350	−24.5
7	79,442	2436.3	− 2567	−130.7	× 55 / 350	−20.5
8	79,443	2469.7	− 2586	−116.3	× 61 / 350	−20.3
Sum, rounded to a whole point						−119

2018 from sb_ca2018_1_csv_v3.zip

Grade	Line in file	Average score	Standard Met	Distance	Students	Weighted
3	79,580	2384.9	− 2436	−51.1	× 48 / 282	−8.7
4	79,583	2400.2	− 2485	−84.8	× 57 / 282	−17.1
5	79,584	2405.7	− 2528	−122.3	× 58 / 282	−25.2
7	79,587	2460.7	− 2567	−106.3	× 59 / 282	−22.2
8	79,588	2436.0	− 2586	−150	× 60 / 282	−31.9
Sum, rounded to a whole point						−105

2019 from sb_ca2019_1_csv_v4.zip

Grade	Line in file	Average score	Standard Met	Distance	Students	Weighted
3	80,093	2400.2	− 2436	−35.8	× 39 / 181	−7.7
4	80,094	2408.9	− 2485	−76.1	× 50 / 181	−21
5	80,095	2398.4	− 2528	−129.6	× 37 / 181	−26.5
8	80,096	2468.6	− 2586	−117.4	× 55 / 181	−35.7
Sum, rounded to a whole point						−91

2022 from sb_ca2022_1_csv_v1.zip

Grade	Line in file	Average score	Standard Met	Distance	Students	Weighted
3	80,368	2327.2	− 2436	−108.8	× 58 / 217	−29.1
4	80,369	2371.1	− 2485	−113.9	× 65 / 217	−34.1
5	80,370	2371.4	− 2528	−156.6	× 94 / 217	−67.8
Sum, rounded to a whole point						−131

2023 from sb_ca2023_1_csv_v1.zip

Grade	Line in file	Average score	Standard Met	Distance	Students	Weighted
3	80,332	2303.1	− 2436	−132.9	× 43 / 166	−34.4
4	80,333	2387.7	− 2485	−97.3	× 56 / 166	−32.8
5	80,334	2376.2	− 2528	−151.8	× 67 / 166	−61.3
Sum, rounded to a whole point						−129

2024 from sb_ca2024_1_csv_v1.zip

Grade	Line in file	Average score	Standard Met	Distance	Students	Weighted
3	80,350	2323.5	− 2436	−112.5	× 49 / 157	−35.1
4	80,351	2399.4	− 2485	−85.6	× 53 / 157	−28.9
5	80,352	2373.7	− 2528	−154.3	× 55 / 157	−54.1
Sum, rounded to a whole point						−118

2025 from sb_ca2025_1_csv_v1.zip

Grade	Line in file	Average score	Standard Met	Distance	Students	Weighted
3	80,014	2363.7	− 2436	−72.3	× 55 / 172	−23.1
4	80,015	2406.2	− 2485	−78.8	× 55 / 172	−25.2
5	80,016	2381.8	− 2528	−146.2	× 62 / 172	−52.7
Sum, rounded to a whole point						−101

Step 2 · The average and the normal range

Average: add the yearly results and divide by how many there are. −95, −104, −119, −105, −91, −131, −129, −118, −101 → −110.3
Typical year-to-year change: how far the result moved from each year to the next, ignoring up or down. 2015→2016: 9 · 2016→2017: 15 · 2017→2018: 14 · 2018→2019: 14 · 2019→2022: 40 · 2022→2023: 2 · 2023→2024: 11 · 2024→2025: 17 → average 15.3
Normal range: multiply the typical change by 2.66, then add it to the average and subtract it. 15.3 × 2.66 = 40.7. Upper limit −69.6, lower limit −151.

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. From 2014–15, 2015–16, 2016–17, 2017–18, 2018–19, 2020–21, 2021–22, 2022–23, 2023–24, 2024–25, 2025–26.