Roberts Ferry Charter School Academy: 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
8	97,455	2485.8	− 2586	−100.2	× 14 / 14	−100.2
Sum, rounded to a whole point						−100

2016 from sb_ca2016_1_csv_v3.zip

Grade	Line in file	Average score	Standard Met	Distance	Students	Weighted
6	90,352	2482.5	− 2552	−69.5	× 19 / 46	−28.7
7	90,355	2520.1	− 2567	−46.9	× 14 / 46	−14.3
8	90,356	2468.8	− 2586	−117.2	× 13 / 46	−33.1
Sum, rounded to a whole point						−76

2017 from sb_ca2017_1_csv_v2.zip

Grade	Line in file	Average score	Standard Met	Distance	Students	Weighted
6	93,005	2516.2	− 2552	−35.8	× 11 / 40	−9.8
7	93,007	2543.7	− 2567	−23.3	× 18 / 40	−10.5
8	93,009	2519.3	− 2586	−66.7	× 11 / 40	−18.3
Sum, rounded to a whole point						−39

2018 from sb_ca2018_1_csv_v3.zip

Grade	Line in file	Average score	Standard Met	Distance	Students	Weighted
6	93,208	2531.4	− 2552	−20.6	× 22 / 50	−9.1
7	93,209	2524.3	− 2567	−42.7	× 12 / 50	−10.2
8	93,212	2520.9	− 2586	−65.1	× 16 / 50	−20.8
Sum, rounded to a whole point						−40

2021 from sb_ca2021_1_csv_v2.zip

Grade	Line in file	Average score	Standard Met	Distance	Students	Weighted
6	91,877	2513.5	− 2552	−38.5	× 22 / 51	−16.6
7	91,878	2494.1	− 2567	−72.9	× 16 / 51	−22.9
8	91,879	2526.9	− 2586	−59.1	× 13 / 51	−15.1
Sum, rounded to a whole point						−55

2022 from sb_ca2022_1_csv_v1.zip

Grade	Line in file	Average score	Standard Met	Distance	Students	Weighted
6	94,097	2510.5	− 2552	−41.5	× 18 / 44	−17
7	94,098	2567.0	− 2567	0	× 15 / 44	0
8	94,099	2529.2	− 2586	−56.8	× 11 / 44	−14.2
Sum, rounded to a whole point						−31

2023 from sb_ca2023_1_csv_v1.zip

Grade	Line in file	Average score	Standard Met	Distance	Students	Weighted
3	94,006	2412.1	− 2436	−23.9	× 23 / 101	−5.4
4	94,007	2533.7	− 2485	48.7	× 23 / 101	11.1
5	94,008	2534.3	− 2528	6.3	× 20 / 101	1.2
6	94,009	2510.5	− 2552	−41.5	× 14 / 101	−5.8
7	94,010	2544.7	− 2567	−22.3	× 21 / 101	−4.6
Sum, rounded to a whole point						−3

2024 from sb_ca2024_1_csv_v1.zip

Grade	Line in file	Average score	Standard Met	Distance	Students	Weighted
3	93,891	2408.9	− 2436	−27.1	× 27 / 126	−5.8
4	93,892	2496.0	− 2485	11	× 23 / 126	2
5	93,893	2545.0	− 2528	17	× 27 / 126	3.6
6	93,894	2552.1	− 2552	0.1	× 18 / 126	0
7	93,895	2539.8	− 2567	−27.2	× 12 / 126	−2.6
8	93,896	2522.8	− 2586	−63.2	× 19 / 126	−9.5
Sum, rounded to a whole point						−12

2025 from sb_ca2025_1_csv_v1.zip

Grade	Line in file	Average score	Standard Met	Distance	Students	Weighted
3	93,619	2438.0	− 2436	2	× 26 / 126	0.4
4	93,620	2521.4	− 2485	36.4	× 25 / 126	7.2
5	93,621	2513.5	− 2528	−14.5	× 21 / 126	−2.4
6	93,622	2553.0	− 2552	1	× 24 / 126	0.2
7	93,623	2569.9	− 2567	2.9	× 17 / 126	0.4
8	93,624	2556.2	− 2586	−29.8	× 13 / 126	−3.1
Sum, rounded to a whole point						3

Step 2 · The average and the normal range

Average: add the yearly results and divide by how many there are. −100, −76, −39, −40, −55, −31, −3, −12, 3 → −39.2
Typical year-to-year change: how far the result moved from each year to the next, ignoring up or down. 2015→2016: 24 · 2016→2017: 37 · 2017→2018: 1 · 2018→2021: 15 · 2021→2022: 24 · 2022→2023: 28 · 2023→2024: 9 · 2024→2025: 15 → average 19.1
Normal range: multiply the typical change by 2.66, then add it to the average and subtract it. 19.1 × 2.66 = 50.8. Upper limit 11.6, lower limit −90.

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.