CCD Data Source Reference

Common Core of Data (CCD) — the federal complete-universe database of all U.S. public K-12 schools and districts (~100,000 schools, ~18,000 districts), collecting enrollment, staffing, finance, and directory data annually (1986-present). Use when analyzing public school enrollment by grade/race/sex, district finances, school staffing, or directory attributes. Public schools and districts only; excludes private schools and postsecondary. Note significant variable encoding and race/ethnicity definition changes over time.

The CCD is the Department of Education's comprehensive, annual, national database of all public elementary and secondary schools and school districts in the United States. It is the only federal dataset that provides a complete universe census (not a sample) of U.S. public K-12 education.

CRITICAL: Value Encoding

The Education Data Portal uses integer codes for categorical variables that differ from NCES's original string codes. Always verify codes against codebooks.

Context	school_type	charter	urban_centric_locale
Portal (integers)	1 (Regular)	0 (No) / 1 (Yes)	11 (City-Large)
NCES original	1-Regular school	Yes / No	11-City: Large

Note: charter and magnet use 0/1 encoding, NOT 1=Yes / 2=No as some NCES documentation shows.

See ./references/variable-definitions.md for complete encoding tables.

What is CCD?

• Primary K-12 database: DOE's authoritative source for public elementary/secondary education statistics
• Universe survey: Covers ALL public schools and districts, not a sample
• Annual collection: Data submitted by State Education Agencies (SEAs) each year
• Six major components: Directory, Membership, Staffing, Finance (state and district), Dropout/Completers
• Coverage: ~100,000 public schools and ~18,000 school districts nationwide
• Historical depth: Data available from 1986 to present (varies by component)
• Collector: National Center for Education Statistics (NCES) via EDFacts
• Mirror coverage (v2 build validated 2026-08-06): Five bulk dataset families; the current versioned mirror (Portal v0.26.1) carries CCD content spanning 1986-2024, with directory and enrollment reaching the 2023-24 school year (file year 2024) while district finance remains at 2020. Mirror publication differs by surface; see Data Access.

Reference File Structure

File	Purpose	When to Read
survey-components.md	Detailed coverage of each CCD survey component	Understanding what data is collected
data-collection.md	How data flows from schools to NCES, timelines, respondent universe	Understanding data provenance and timing
variable-definitions.md	Key variables, coding schemes, special values	Interpreting specific data elements
data-quality.md	Missing data patterns, suppression, state variations	Assessing data reliability
historical-changes.md	Definition changes, code revisions over time	Longitudinal analysis

Decision Trees

What CCD component do I need?

What information do you need?
├─ School/district names, addresses, contacts → Directory
│   └─ See ./references/survey-components.md#directory
├─ Student enrollment counts → Membership
│   ├─ By grade → Membership (grade disaggregation)
│   ├─ By race/ethnicity → Membership (race disaggregation)
│   ├─ By sex → Membership (sex disaggregation)
│   └─ See ./references/survey-components.md#membership
├─ Staff/teacher counts → Staffing
│   └─ See ./references/survey-components.md#staffing
├─ Revenue and expenditure → Finance
│   ├─ State-level totals → National Public Education Financial Survey
│   ├─ District-level detail → School District Finance Survey (F-33)
│   └─ See ./references/survey-components.md#finance
├─ Graduation/dropout rates → Dropout and Completers
│   └─ See ./references/survey-components.md#dropout-completers
└─ School type, charter status, locale → Directory
    └─ See ./references/survey-components.md#directory

Is this a data quality issue?

Unexpected data values?
├─ Negative numbers (-1, -2, -3, -9) → Missing data codes
│   └─ See ./references/variable-definitions.md#missing-data-codes
├─ Very different from prior year → Check for definition changes
│   └─ See ./references/historical-changes.md
├─ State appears as outlier → Check state-specific reporting
│   └─ See ./references/data-quality.md#state-variations
├─ Large number of zeros → Check suppression rules
│   └─ See ./references/data-quality.md#suppression
└─ Locale codes don't match → Pre/post 2006 locale system change
    └─ See ./references/historical-changes.md#locale-codes

Can I compare across time?

Building a time series?
├─ Race/ethnicity categories → Major change in 2010
│   └─ See ./references/historical-changes.md#race-ethnicity
├─ Locale codes → Completely revised in 2006
│   └─ See ./references/historical-changes.md#locale-codes
├─ School/district IDs → Check for ID changes
│   └─ See ./references/variable-definitions.md#identifiers
├─ Free/reduced lunch → CEP and direct certification changes
│   └─ See ./references/data-quality.md#frpl
└─ Finance data → Definition changes and inflation
    └─ See ./references/historical-changes.md#finance

Quick Reference: CCD Components

Component	Level	Key Variables	Years	Update Cycle
Directory	School, LEA, State	Name, address, type, status, locale, charter	1986+	Annual
Membership	School, LEA, State	Enrollment by grade, race, sex	1986+	Annual
Staffing	School, LEA, State	FTE teachers, staff by category	1987+	Annual
Finance (State)	State	Revenue, expenditure by source/function	1989+	Annual (1-2 yr lag)
Finance (District)	LEA	Revenue, expenditure, per-pupil	1989+	Annual (2 yr lag)
Dropout/Completers	LEA, State	Dropout counts, diploma recipients	1991+	Annual

Note: Not all components listed above are available through the Portal mirrors. See the Data Access section for which datasets are mirrored.

Key Identifiers

Portal Column	Format	Level	Example	Notes
ncessch	12 characters	School	010000100100	State FIPS (2) + LEA suffix (5) + School (5)
leaid	7 characters	District	0100001	State FIPS (2) + State-assigned (5)
fips	2 digits	State	01	Federal Information Processing Standard

Identifier-width requirement (an analysis-time normalization contract, not a raw-file guarantee): Treat ncessch and leaid as identifiers, not quantities. At analysis time, validate nonmissing, nonsentinel ncessch as a numeric string of exactly 12 characters and leaid as a numeric string of exactly 7 characters before joining.

The current v2 mirror (validated 2026-08-06) has no universal identifier contract — per-file id typing is heterogeneous, so this width rule describes how you must normalize on read, not what the raw files contain. Observed reality: leaid is native-width String (including alphanumeric values such as 06D0004, widths 2-7) in districts_ccd_finance, but Int64 in school-districts_lea_directory and districts_saipe. Integer storage cannot preserve leading zeros or display-width semantics, so an Int64 leaid/ncessch must be cast to a zero-padded string before width validation. Inspect the actual file schema and normalize to validated strings explicitly; never assume a uniform id dtype across CCD files. See variable-definitions.md for the per-file detail and the canonical materialization rules.

Missing Data Codes

The Portal uses both null and negative integer codes to represent missing/special values. The specific pattern varies by dataset:

Code	Meaning	When Used
null	Not available	Common in Directory fields that don't apply to all years
-1	Missing/not reported	Data not reported by state
-2	Not applicable	Item doesn't apply to this entity
-3	Suppressed	Data suppressed for privacy
-9	Not reported	State did not report this item

Check actual data. Some datasets use null where others use -1 for effectively the same condition. Always check the observed values in the data before applying a blanket missing-value filter.

School Types (school_type)

Code	Type	Description
1	Regular	Standard public school
2	Special Education	Focuses on students with disabilities
3	Vocational	Career/technical education focus
4	Alternative	Non-traditional programs
5	Reportable Program	Program within another school (2007-08+)

LEA Types (agency_type)

Code	Type	Description
1	Regular	Locally governed school district
2	Component	District sharing superintendent with others
3	Supervisory Union	Admin services for multiple districts
4	Regional Agency	Education service agency
5	State-operated	State-run schools (deaf, blind, correctional)
6	Federal-operated	Federal schools (BIE, DoDEA)
7	Charter Agency	All schools are charters (2007-08+)
8	Other	Doesn't fit other categories (2007-08+)
9	Specialized Agency	Specialized public agency (observed in data)

Grade -1 Encoding

In CCD enrollment data:

• grade = -1 means Pre-Kindergarten, NOT missing data
• grade = 99 means Total across all grades

Do NOT filter grade >= 0 — this removes all Pre-K students!

# WRONG - removes Pre-K students!
df = df.filter(pl.col("grade") >= 0)

# CORRECT
pre_k = df.filter(pl.col("grade") == -1)  # Pre-K only
k12 = df.filter(pl.col("grade").is_between(0, 12))  # K-12
total = df.filter(pl.col("grade") == 99)  # All grades

# R equivalent
library(dplyr)

# WRONG - removes Pre-K students!
df <- df |> filter(grade >= 0)

# CORRECT
pre_k <- df |> filter(grade == -1)              # Pre-K only
k12 <- df |> filter(grade >= 0, grade <= 12)    # K-12
total <- df |> filter(grade == 99)              # All grades

Portal Column Name Mapping

Variable Name Mapping: The Portal column urban_centric_locale contains locale codes. Some documentation may refer to this as simply locale. Use urban_centric_locale when filtering or selecting columns in Portal data.

Dataset-to-Component Mapping

Mirror Dataset	CCD Component	Path
Schools CCD Directory	School Directory	ccd/schools_ccd_directory
Schools CCD Enrollment	School Membership	ccd/schools_ccd_enrollment_{year}
Districts LEA Directory	LEA Directory	ccd/school-districts_lea_directory
Districts CCD Enrollment	LEA Membership	ccd/schools_ccd_lea_enrollment_{year}
Districts CCD Finance	F-33 District Finance	ccd/districts_ccd_finance

Data Collection Flow

Schools → Local Education Agencies (LEAs)
                ↓
    State Education Agencies (SEAs)
                ↓
        EDFacts Submission System
                ↓
    NCES Quality Review & Editing
                ↓
        CCD Public Data Files

Timeline: Data for school year 20XX-YY typically submitted spring 20YY, released fall 20YY (preliminary) to spring 20YY+1 (provisional/final).

Data Access

Data for the 2023-24 school year (file year 2024) is available. The current versioned mirror (Portal v0.26.1, v2 build validated 2026-08-06) carries CCD content spanning 1986-2024: directory and enrollment reach file year 2024, while district finance remains at 2020. See datasets-reference.md for canonical paths, mirrors.yaml for mirror configuration, and fetch-patterns.md for fetch code patterns.

Key datasets (5 dataset families; see datasets-reference.md for the authoritative list):

Dataset	Type / coverage (v2 mirror, 2026-08-06)	Path	Codebook
School Directory	Single, through 2024	ccd/schools_ccd_directory	ccd/codebook_schools_ccd_directory
School Enrollment	Yearly, 1986-2024	ccd/schools_ccd_enrollment_{year}	ccd/codebook_schools_ccd_enrollment
District Directory	Single, through 2024	ccd/school-districts_lea_directory	ccd/codebook_districts_ccd_directory
District Enrollment	Yearly, 1986-2024	ccd/schools_ccd_lea_enrollment_{year}	ccd/codebook_districts_ccd_enrollment
District Finance	Single, through 2020	ccd/districts_ccd_finance	ccd/codebook_districts_ccd_finance

Verification sources: The 1986-2024 span (finance at 2020) is confirmed by the v2 mirror build validation (content-based year table, 2026-08-06). The underlying declaration sources — Portal endpoint catalog, Portal bulk manifest, and NCES CCD files — were last consulted 2026-07-27. Catalog years and labels are declarations; verify actual rows/files for the selected surface.

Not in Portal mirrors: The following CCD components are documented in this skill for reference but are not available through the Education Data Portal mirrors:

• Dropout/Completers — completion and dropout data by demographics
• State Finance (NPEFS) — state-level education revenue and expenditure

For these components, access NCES directly at https://nces.ed.gov/ccd/.

Codebooks are .xls files co-located with data in all mirrors. Use get_codebook_url() from fetch-patterns.md to construct download URLs:

url = get_codebook_url("ccd/codebook_schools_ccd_directory")

# R equivalent -- get_codebook_url() is a Python helper; construct the URL directly
# Mirror failover: see education-data-query/references/fetch-patterns.md (R pattern)
mirrors <- yaml::read_yaml("mirrors.yaml")
url <- paste0(mirrors$mirrors[[1]]$root_url, "ccd/codebook_schools_ccd_directory.xls")

Truth Hierarchy: When interpreting variable values, apply this priority:

1. Actual data file (what you observe in the parquet/CSV) -- this IS the truth
2. Live codebook (.xls in mirror) -- authoritative documentation, may lag
3. This skill documentation -- convenient summary, may drift from codebook

If this documentation contradicts the codebook, trust the codebook. If the codebook contradicts observed data, trust the data and investigate.

Filtering

All filtering is done locally with Polars after download:

import polars as pl

# Filter by state (California)
df = df.filter(pl.col("fips") == 6)

# Filter by year
df = df.filter(pl.col("year").is_in([2020, 2021, 2022]))

# Get totals only (enrollment)
df = df.filter(pl.col("grade") == 99)

# Get specific grades (K-12)
df = df.filter(pl.col("grade").is_between(0, 12))

# R equivalent
library(dplyr)

# Filter by state (California)
df <- df |> filter(fips == 6)

# Filter by year
df <- df |> filter(year %in% c(2020, 2021, 2022))

# Get totals only (enrollment)
df <- df |> filter(grade == 99)

# Get specific grades (K-12)
df <- df |> filter(grade >= 0, grade <= 12)

Finance Data Notes

• Finance coverage: District finance (districts_ccd_finance) reaches 2020 in the v2 mirror (build validated 2026-08-06; the file was byte-stable content between the v0.24.0 and v0.26.1 vintages). Treat that as a dated Portal-surface cutoff, not a timeless statement about current NCES files.
• Finance dataset has 163 columns -- by far the most complex CCD dataset
• Some finance columns use _total suffix (e.g., exp_current_instruction_total)
• leaid is String type in Finance data (unlike the Districts Directory where it is Int64)

API vs. Bulk Representation

• teachers_fte precision differs by delivery channel (verified 2026-08-07): the live Portal API serves teachers_fte (school directory) integer-rounded, while bulk-file-derived data (and the mirror) carries 2-decimal precision — cell-exact against the bulk CSV (e.g., 28.98 in the CSV and mirror vs. 28.0 returned by the API). API and bulk representations can differ even at the same Portal version, so prefer the bulk/mirror value when precision matters and note the source channel when reporting.

Common Pitfalls

Pitfall	Issue	Solution
Summing grades	Misses ungraded students	Use grade=99 (total) instead
Assuming -1 is missing	In enrollment grade data, -1 = Pre-K	Check variable format in codebook
Reading highest_grade_offered == -1 as a grade	In directory grade-span (GSLO/GSHI), -1 = MISSING, not Pre-K/≥9	Exclude -1 before grade-span filters (see variable-definitions.md)
Cross-state comparison	Different state definitions	Check state methodology first
Using FRPL as poverty measure	CEP schools show 100%	Supplement with MEPS or SAIPE data
Locale time series	2006 code system change	Analyze pre/post-2006 separately
Charter school counts	Early years incomplete	Verify against state records pre-2010
Dropout rate comparison	State definitions vary	Within-state comparisons only
Using NCES string codes	Portal uses integers	See variable-definitions.md for mappings
Assuming charter=1/2	Portal uses 0=No, 1=Yes	Empirically verified; not NCES 1=Yes, 2=No
Identifier type/width across files	Prior HF Parquet objects may expose integer leaid/ncessch, losing leading-zero/display-width semantics	Normalize to strings; validate leaid length 7 and ncessch length 12 before joining

Coverage Notes

What CCD Includes

• All public schools (traditional, charter, magnet, alternative)
• All public school districts and LEAs
• Bureau of Indian Education (BIE) schools
• Department of Defense Education Activity (DoDEA) schools
• State-operated schools (deaf, blind, correctional)

What CCD Excludes

• Private schools (use Private School Universe Survey - PSS)
• Homeschool students
• Postsecondary institutions (use IPEDS)
• Detailed student-level data (CCD is aggregate only)

Related Data Sources

Source	Relationship	When to Use
education-data-source-edfacts	CCD nonfiscal data flows through EDFacts	Same underlying data
education-data-source-crdc	Biennial; uses CCD school IDs	Need discipline, course access, equity data
education-data-source-saipe	Uses CCD district IDs	Need poverty estimates (better than FRPL)
education-data-source-meps	School-level poverty estimates	Need school-level poverty (better than FRPL)
education-data-source-ipeds	Separate system for postsecondary	Need college/university data
PSS	Private school equivalent	Need private school data
education-data-source-nhgis	Census geography crosswalks	Need school-Census links
education-data-explorer	Parent discovery skill	Finding available datasets
education-data-query	Data fetching (mirror system)	Downloading parquet/CSV files via fetch_from_mirrors()

Topic Index

Topic	Reference File
Directory survey	./references/survey-components.md
Membership survey	./references/survey-components.md
Staffing survey	./references/survey-components.md
Finance surveys	./references/survey-components.md
Dropout/completers	./references/survey-components.md
Data collection process	./references/data-collection.md
EDFacts submission	./references/data-collection.md
Respondent universe	./references/data-collection.md
NCES identifiers	./references/variable-definitions.md
Missing data codes	./references/variable-definitions.md
Grade codes	./references/variable-definitions.md
Race/ethnicity codes	./references/variable-definitions.md
Locale codes	./references/variable-definitions.md
State-level variations	./references/data-quality.md
Missing data patterns	./references/data-quality.md
FRPL limitations	./references/data-quality.md
Data suppression	./references/data-quality.md
Locale code changes (2006)	./references/historical-changes.md
Race/ethnicity changes (2010)	./references/historical-changes.md
LEA type changes (2007)	./references/historical-changes.md
ID changes over time	./references/historical-changes.md