121 School Index methodology — v3

The 121 School Rating summarizes evidence for an individual school; it is not an official state rating, an address-assignment claim, or an enrollment guarantee.

For elementary and middle schools, Academic Achievement has 65% weight, Academic Improvement 25%, and Attendance 10%.

For high schools, Academic Achievement has 40% weight, College/Career Readiness 30%, Academic Improvement 20%, and Attendance 10%.

• Academic Achievement: the school-level percentile of published California distance-from-standard status for English language arts and mathematics.
• Academic Improvement: the school-level percentile of published year-over-year change in distance-from-standard status. This is not a longitudinal growth model.
• College/Career Readiness: the school-level percentile of the published prepared percentage for eligible high-school cohorts.
• Attendance: the school-level percentile of published chronic-absence evidence, oriented so lower absence is stronger.

Available component percentiles are multiplied by the weights for the school level and summed into an absolute 0–100 indicator score. Missing eligible components are reweighted proportionally only when at least 60% of eligible weight is observed.

The public 1–10 rating uses fixed bands so the same score means the same rating across releases: 90–100 is 10/10, 80–89 is 9/10, continuing in ten-point bands, and 0–9 is 1/10.

Fixed bands are not statewide quotas. A rating can change when a school’s official evidence or its within-level component percentiles change, not because a named competitor score was imported.

• The 0–100 indicator score, component percentiles, school year, coverage, and confidence are displayed with the rating.
• Academic Achievement is deliberately the largest component at every school level.
• No third-party school rating is an input, target, calibration label, or override.

Component percentiles compare schools only within the same school level and only when the comparable cohort and published sample meet v3 minimums.

Alternative, continuation, special-education, adult, primarily virtual, closed, and otherwise non-comparable records do not receive a numeric indicator.

Subgroup missingness and score distributions are release checks, not public subgroup ratings. Material gaps require release-bound independent adjudication and public disclosure when approval is granted.

• Minimum component sample: 20 students.
• Minimum comparison cohort: 20 schools.
• Minimum observed eligible weight: 60%.

Source bytes are stored as immutable, checksummed release artifacts from the California Department of Education and the National Center for Education Statistics.

The registered California Dashboard chronic-absence indicator covers TK–8, so Attendance is generally absent for high schools and the observed high-school components are reweighted with disclosed coverage.

The rating does not measure every aspect of a school. Attendance boundaries, transfers, choice programs, charters, magnets, capacity, and enrollment rules can change independently and must be confirmed with the district.

Registered sources are checked monthly. Candidate releases are normally rebuilt annually when official source versions change. Version v3 is permanent and is never silently rewritten into another method.

• Corrections require a new checksummed release and validation report.
• Previously approved releases remain available for rollback and audit.

• California Department of Education data and reports
• National Center for Education Statistics

Machine-readable document: /methodology/121-school-index/v3.json.