Two sources of data are available to measure enrolment rates:
On a five-yearly basis, the count of persons aged 6–15 years from the ABS Census of Population and Housing who are reported as attending a school is divided by the total persons in that age group (excluding any item non-responses).
On an annual basis, the National Schools Statistics Collection (NSSC) counts the number of students enrolled in all schools in Australia. This is collected through the schools census undertaken in the first week of August. This count is divided by the Estimated Resident Population (ERP) as at June 30 in that year sourced from the ABS.
From 2019, the annual measure based on the NSSC is no longer reported as a Key Performance Measure (KPM 1(a) Enrolment). The measure based on the ABS Census remains the KPM. The KPM is specified as the number of students aged 6–15 years enrolled in school, expressed as a proportion of the 6–15-year-old population. As this approximates the age range of students for whom schooling is compulsory, the enrolment rate for this group is close to 100%.