Strobridge 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	1,586	2375.2	− 2436	−60.8	× 107 / 345	−18.9
4	1,587	2421.9	− 2485	−63.1	× 75 / 345	−13.7
5	1,590	2415.5	− 2528	−112.5	× 86 / 345	−28
6	1,591	2447.0	− 2552	−105	× 77 / 345	−23.4
Sum, rounded to a whole point						−84

2016 from sb_ca2016_1_csv_v3.zip

Grade	Line in file	Average score	Standard Met	Distance	Students	Weighted
3	1,390	2377.5	− 2436	−58.5	× 66 / 336	−11.5
4	1,393	2413.0	− 2485	−72	× 106 / 336	−22.7
5	1,395	2438.2	− 2528	−89.8	× 80 / 336	−21.4
6	1,396	2441.8	− 2552	−110.2	× 84 / 336	−27.6
Sum, rounded to a whole point						−83

2017 from sb_ca2017_1_csv_v2.zip

Grade	Line in file	Average score	Standard Met	Distance	Students	Weighted
3	1,429	2378.0	− 2436	−58	× 89 / 318	−16.2
4	1,430	2429.1	− 2485	−55.9	× 62 / 318	−10.9
5	1,433	2427.9	− 2528	−100.1	× 94 / 318	−29.6
6	1,434	2456.4	− 2552	−95.6	× 73 / 318	−21.9
Sum, rounded to a whole point						−79

2018 from sb_ca2018_1_csv_v3.zip

Grade	Line in file	Average score	Standard Met	Distance	Students	Weighted
3	1,458	2385.5	− 2436	−50.5	× 70 / 312	−11.3
4	1,460	2406.3	− 2485	−78.7	× 83 / 312	−20.9
5	1,462	2431.0	− 2528	−97	× 64 / 312	−19.9
6	1,464	2458.4	− 2552	−93.6	× 95 / 312	−28.5
Sum, rounded to a whole point						−81

2019 from sb_ca2019_1_csv_v4.zip

Grade	Line in file	Average score	Standard Met	Distance	Students	Weighted
3	1,485	2382.9	− 2436	−53.1	× 72 / 281	−13.6
4	1,486	2398.8	− 2485	−86.2	× 63 / 281	−19.3
5	1,487	2405.4	− 2528	−122.6	× 79 / 281	−34.5
6	1,488	2446.8	− 2552	−105.2	× 67 / 281	−25.1
Sum, rounded to a whole point						−92

2022 from sb_ca2022_1_csv_v1.zip

Grade	Line in file	Average score	Standard Met	Distance	Students	Weighted
3	1,469	2378.9	− 2436	−57.1	× 49 / 213	−13.1
4	1,470	2394.5	− 2485	−90.5	× 58 / 213	−24.6
5	1,471	2393.8	− 2528	−134.2	× 49 / 213	−30.9
6	1,472	2430.7	− 2552	−121.3	× 57 / 213	−32.5
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. −84, −83, −79, −81, −92, −101 → −86.7
Typical year-to-year change: how far the result moved from each year to the next, ignoring up or down. 2015→2016: 1 · 2016→2017: 4 · 2017→2018: 2 · 2018→2019: 11 · 2019→2022: 9 → average 5.4
Normal range: multiply the typical change by 2.66, then add it to the average and subtract it. 5.4 × 2.66 = 14.4. Upper limit −72.3, lower limit −101.1.

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.