Methodology

The data layers

1. Source files are fetched from publishers, recorded with sha256 + retrieved-at provenance, and inspected. Source registry: docs/cities/philly/sources.yaml.
2. Loaders normalize the wide / long / zip-archived source rows into long-format facts in philly_school_year_metrics. Most metrics carry a population_cut of n/a; PSSA and Keystone carry both acct (accountability cohort) and actual cuts.
3. Peer groups are derived as the up-to-40 nearest neighbors on demographic shares (race composition, English learners, special education, and economic disadvantage), with hard filters on school level, admission category, and sector — so a charter school is only ever compared with other charters, and a district-run school with district-run schools. The district publishes no English-learner or economic-disadvantage shares for charter schools, so charter peer distances use the five shares available rather than seven. 287 of the 331 schools in the directory get a peer group (210 of 230 district-run, 64 of 81 charter, 13 of 19 contracted); the rest are dropped because their filtered universe has fewer than 5 candidate peers.
4. Percentiles are computed both citywide (every default-included school) and within peer group. Direction-adjusted: for lower-is-better metrics (the out-of-school suspension rates), the ranking is flipped so a high percentile always means a good outcome. Attendance is served as the share attending 90%+ of days (higher is better); the chronic-absenteeism analysis reports its complement.

Analyses

Chronic absenteeism in Philadelphia schools — five years of district data, a charter comparison on the state’s measure, and 2025-26 month by month, with every figure traceable to its source. Definitions and limitations: the metric methodology page.

Trace any number

Every value served on the Philadelphia pages has a proof tree: the publisher’s file it came from (identified by cryptographic hash), the script that read it, the arithmetic and algorithms applied, the checks it passed, and the assumptions involved. Values with a dotted underline on the Outliers, Movers, and school pages link straight to their tree; the full index is at /philly/proof.

What “validated” means

Each loaded metric is run through a four-check taxonomy before it's eligible to be served:

• (i) Completeness — does every (school, year) cell in the source appear in the served DB?
• (ii) Base case — does the served value match an independent re-read of the exact ingested file at ±1.0 pp tolerance? The binding gate.
• (iii-a) SPREE spot check— vs SDP's published family-facing per-school report. 616 of 616 paired cells match within tolerance.
• (iii-b) Future Ready cross-check — vs the independent-publisher PDE Future Ready PA Index file.
• (iv) Computed values — derived metrics (out-of-school suspension distribution rollups, PSES topic rollups, demographic shares) against their raw components. OSS 8,034/8,034 match; PSES 8,157/8,157 match.

Plus an Acct vs Actual population-cut diff specific to Pennsylvania's dual reporting cuts. The Acct cut is canonical for the rankings; the Actual cut is loaded alongside so the diff stays inspectable.

Reports written by the harness live under docs/qa_reports/philly/. Current results: (i) PASS, (ii) PASS at ±1.0 pp across 6 components (837 paired cells, zero mismatches). Acct vs Actual is byte-identical across all 4,535 paired cells for 2024-25 at the school-rollup grain (the harness keeps both load paths so future divergence surfaces immediately).

Decisions of record

Eight design decisions (O.1 through O.8) are settled and documented in docs/cities/philly/00_overview.md. Highlights: SDP is the canonical publisher for outcomes when available; PSES teacher and student instruments are both first-class; PVAAS growth is a first-class metric alongside proficiency; the Acct cohort cut is canonical for PSSA.

Source URLs

• Future Ready PA Index data files (PDE) — PSSA, Keystone, PVAAS growth, ESSA designations.
• OpenDataPhilly — SDP PSSA & Keystone — district and alternative schools, grade × subgroup detail.
• OpenDataPhilly — Philadelphia School Experience Survey (PSES).
• OpenDataPhilly — SDP graduation, attendance, suspensions.