SOURCES AND METHODOLOGY POLICY

Source hierarchy

Primary sources are preferred for statistical claims. Common source categories include:

1. Federal statistical agencies and official federal education datasets.
2. State education departments and other state government agencies.
3. Public university systems and official institutional reporting offices.
4. Peer-reviewed research and established nonprofit research organizations.
5. Secondary reference material used only for context or source discovery.

When the same indicator is available from multiple agencies, the selected source should be based on definition, reporting period, geographic coverage, release status and comparability rather than convenience alone.

Source identification

A statistical page should identify enough information for the underlying data to be located and evaluated. Relevant details may include:

• Publishing agency.
• Dataset or report name.
• Table, file or indicator name.
• Reporting period.
• Publication or release date.
• Release status, such as preliminary, provisional, revised or final.
• Geographic coverage.
• Important exclusions or suppressed values.

Reporting periods and page dates

The year in a page title may represent the edition or review year rather than the year in which the underlying activity occurred. Education datasets are often released months or years after the reporting period ends.

The applicable data year should therefore be displayed near the principal table, chart or summary. A page labeled as a current edition should not imply that every value was collected during the edition year.

Metric definitions

Each core indicator should have a stable internal definition. The definition should address:

• The population or institutions included.
• Grade or age coverage.
• Public, private, charter or postsecondary coverage.
• The reporting date or fiscal year.
• Whether the value is a headcount, membership count, full-time equivalent or estimate.
• The numerator and denominator used for rates or ratios.
• Whether values are nominal, inflation-adjusted or regionally adjusted.

Values with materially different definitions should not be merged into one comparison table without an explanatory distinction.

Geographic coverage

State-level tables may include the 50 states and the District of Columbia. U.S. territories, Department of Defense schools, Bureau of Indian Education schools or other jurisdictions may be included only when the source supports a comparable measure and the scope is clearly stated.

The word “state” may occasionally be used as a practical label for a table containing the District of Columbia. The precise geographic coverage should remain visible in the methodology section.

Data transformations

Source values may be transformed to improve comparison or readability. Common transformations include:

• Calculating percentage change.
• Converting totals to per-student or per-capita values.
• Grouping values into ranges.
• Calculating averages, medians and ratios.
• Sorting values and assigning ranks.
• Rounding values for display.

Transformations should not change the meaning of the original measure. Calculations should be reproducible from the identified inputs whenever practical.

Rounding

Displayed values may be rounded for readability. Totals calculated from displayed rounded values may differ slightly from totals calculated from the underlying unrounded data.

Ranking should use a stated rule. When ranks are based on unrounded values but the table displays rounded values, apparently equal values may receive different ranks. That distinction should be disclosed.

Missing, suppressed and unavailable values

A missing value is not automatically equal to zero. Depending on the source, a blank, dash, symbol or special code may indicate that the value was:

• Not reported.
• Not applicable.
• Suppressed for privacy or statistical reliability.
• Unavailable at the time of publication.
• Excluded because it was not comparable.

Such values should be labeled and should not be included in averages or rankings unless the methodology explicitly supports their inclusion.

Preliminary and revised data

Preliminary or provisional data may be used when it is the most recent available release and its status is clearly identified. Final data should normally replace provisional values after publication when the definitions remain comparable.

A revision by the original source may change historical values. A later page update does not necessarily indicate that the earlier value was reported incorrectly; it may reflect an official source revision.

Comparability limitations

Comparisons may be limited by differences in reporting practices, accounting rules, enrollment definitions, assessment participation, institutional structures or collection schedules.

Where comparability is uncertain, the page may include a caution, exclude affected values from ranking or present them in a separate group.

Quality checks

Quality review may include:

• Confirming the expected number of geographic rows.
• Testing that percentages and category totals are internally consistent.
• Comparing text summaries with table values.
• Checking extreme values against the source.
• Reviewing duplicate, missing or mislabeled jurisdictions.
• Confirming that the displayed source year matches the underlying file.
• Checking whether a newer or revised release has replaced the cited version.

Citations and source access

Links to original sources may be provided when suitable. A source link does not imply that the source agency has reviewed or endorsed US School Index.

External source URLs may change. The source agency, dataset name and reporting period remain important identifiers when a direct link is no longer available.

Methodology questions

Questions about a source, definition or calculation can be submitted to support@usschoolindex.org. The page URL and disputed metric should be included.