education.attendance-rate

export function attendanceRate(possibleSessions: number, missedSessions: number, onDate: string): AttendanceRate

/** Attendance, absence and the DfE absence flags for one pupil. */
export interface AttendanceRate {
  /** 10000 minus absenceBasisPoints */
  readonly attendanceBasisPoints: number;
  /** missed / possible, rounded half-up to a basis point */
  readonly absenceBasisPoints: number;
  /** missed 10% or more of possible sessions */
  readonly persistentlyAbsent: boolean;
  /** missed 50% or more; null on a date before that measure was published */
  readonly severelyAbsent: boolean | null;
}

import { attendanceRate } from "#fune/education.attendance-rate@^1";

import { parseIsoDate } from "./dates_add_days.ts";  ← from dates.add-days ^1.0.0 · built alongside by fune
import { roundDiv } from "./math_round_div.ts";  ← from math.round-div ^1.0.0 · built alongside by fune
import { ABSENCE_THRESHOLDS, ABSENCE_THRESHOLDS_HISTORY, ABSENCE_THRESHOLDS_HORIZON } from "./education_attendance_rate_data.ts";  ← this capability’s own data, compiled from data/absence-thresholds.json into the same file by fune build
import { type AttendanceRate } from "./education_attendance_rate_types.ts";

function thresholdOn(measure: string, onDate: string): number | null {
  for (const r of ABSENCE_THRESHOLDS) {
    if (r.measure === measure && onDate >= r.validFrom && (r.validTo === null || onDate <= r.validTo)) return r.basisPoints;
  }
  return null;
}

/**
 * Attendance and absence in basis points, and the DfE absence flags.
 *
 * The flags compare missed x 10000 with possible x threshold, exactly: a rate
 * of 9.996% rounds to 10.00% but is not persistent absence.
 */
export function attendanceRate(possibleSessions: number, missedSessions: number, onDate: string): AttendanceRate {
  if (!Number.isInteger(possibleSessions) || possibleSessions < 1) {
    throw new RangeError(`possibleSessions must be a whole number of 1 or more, received ${possibleSessions}`);
  }
  if (!Number.isInteger(missedSessions) || missedSessions < 0 || missedSessions > possibleSessions) {
    throw new RangeError(`missedSessions must be a whole number from 0 to possibleSessions (${possibleSessions}), received ${missedSessions}`);
  }
  parseIsoDate(onDate);
  const persistent = thresholdOn("persistent", onDate);
  if (persistent === null) {
    if (ABSENCE_THRESHOLDS_HISTORY !== "full" && ABSENCE_THRESHOLDS_HORIZON !== null && onDate < ABSENCE_THRESHOLDS_HORIZON) {
      throw new RangeError(
        `no persistent absence definition on ${onDate}: this build was installed with history=${ABSENCE_THRESHOLDS_HISTORY}, so it only carries rules from ${ABSENCE_THRESHOLDS_HORIZON}. Reinstall with history=full for earlier years.`,
      );
    }
    throw new RangeError(`no persistent absence definition on ${onDate}`);
  }
  const severe = thresholdOn("severe", onDate);
  const absence = roundDiv(missedSessions * 10000, possibleSessions, "half-up");
  return {
    attendanceBasisPoints: 10000 - absence,
    absenceBasisPoints: absence,
    persistentlyAbsent: missedSessions * 10000 >= possibleSessions * persistent,
    severelyAbsent: severe === null ? null : missedSessions * 10000 >= possibleSessions * severe,
  };
}

Install

fune build

With that line in your source, in a TypeScript project (language typescript in fune.project), fune build resolves it and its 2 dependencies, pins them in fune.lock, downloads only the TypeScript package of each, and builds the code above into your project’s .fune/build, one readable file per capability with a header linking back here. Or pin a range in fune.project and build in one step:

fune add education.attendance-rate

The manifest, vectors and README with only the TypeScript implementation. Install it without the registry with fune add ./education.attendance-rate-1.0.1-typescript.fune, or fetch it from a terminal with fune pull education.attendance-rate@1.0.1:typescript.

The whole function, every language, is one file too: education.attendance-rate-1.0.1.fune, 20,274 bytes, sha256 628cb864d801b56920bd73fdf860b8bf0b0145e5019b166523a736ed57a86b22. It installs into a project of any language.

// fune: before education.attendance-rate

// fune: after education.attendance-rate

// fune: replace dates.add-days in education.attendance-rate
// fune: replace math.round-div in education.attendance-rate

// fune: step education.attendance-rate after <n|label>

More from the author

- **Persistent absence**: missing 10% or more of the pupil's own possible sessions. This is the definition from the 2015/16 academic year. It was introduced in 2005/06 at 20%, and from 2010/11 was about 15% measured against a standard number of sessions rather than the pupil's own, which cannot be expressed as a percentage of one pupil's sessions; a date before 1 September 2015 is therefore refused rather than answered with today's rule. - **Severe absence**: missing 50% or more. The data carries it from the 2018/19 academic year, the first year for which the DfE statistics release reports it; before 1 September 2018 `severelyAbsent` is null.

Both are dated rows in `data/absence-thresholds.json`, and `onDate` picks the row in force.

## Decisions

- **The flags use the exact fraction.** A pupil who missed 250 of 2,501 sessions has an absence rate of 9.996%, which rounds to 1000 basis points, but is not persistently absent: 250 is less than 10% of 2,501. Comparing the rounded rate is the naive mistake; a vector pins it. - **Absence is rounded, attendance is derived.** Absence is rounded half-up to a basis point and attendance is 10000 minus that, so the two always add up to 100%. (Rounding both half-up gives 10001 when each sits on a half.) - Sessions are whatever the school counts: two per day (morning and afternoon) in England. Missed sessions include authorised and unauthorised absence, as the DfE measures do; pass only the sessions you want counted. - No possible sessions is an error: there is no rate to report.

## Sources

- Department for Education, "Pupil absence statistics: methodology" (Explore education statistics): definitions of persistent absence (10% or more of a pupil's own possible sessions, from 2015/16) and severe absence (50% or more), and the history of the persistent absence threshold: https://explore-education-statistics.service.gov.uk/methodology/pupil-absence-statistics-methodology - Department for Education, "Pupil absence in schools in England: 2018/19", the first release reporting severe absence: https://explore-education-statistics.service.gov.uk/find-statistics/pupil-absence-in-schools-in-england/2018-19

## Notices

Contains public sector information licensed under the Open Government Licence v3.0 (https://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/).

1.0.1 adds its attribution notices (NOTICE). The code and the tests are unchanged.

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