To show the overall level of development of an educational system in terms of the average number of years of schooling that the education system offers to the eligible population, including those who never enter school.

Enrolment by age and of age unknown at all levels of education; population by single years of age; or, alternatively, the age-specific enrolment ratios for all levels of education.

By level of education and by sex.

Total number of years of schooling that a person of a certain age can expect to receive in the future, assuming that the probability of his or her being enrolled in school at any particular age is equal to the current enrolment ratio for that age.

For a child of a certain age a, the school life expectancy is calculated as the sum of the age specific enrolment rates for the levels of education specified. The part of the enrolment that is not distributed by age is divided by the school-age population for the level of education they are enrolled in, and multiplied by the duration of that level of education. The result is then added to the sum of the age-specific enrolment rates.

The calculation of this indicator requires complete and reliable data on enrolment and population by single-years of age corresponding to all levels of education for the entire duration of schooling, including tertiary education.

The UIS sets standards, develops questionnaires and quality control protocols for country data reporting, and maintains the global database on the structure of education and enrolment data. The United Nations Population Division (UNPD) produces and maintains population data. National population data that comply with UIS quality standards can also be used.

Interpretations

A relatively high SLE indicates greater probability for children to spend more years in education and higher overall retention within the education system. It must be noted that the expected number of years does not necessarily coincide with the expected number of grades of education completed, because of repetition. Since school life expectancy is an average based on participation in different levels of education, the expected number of years of schooling may be pulled down by the magnitude of children who never go to school. Those children who are in school may benefit from many more years of education than the average.

Limitations

Caution is required when making cross-country comparisons; neither the length of the academic year nor the quality of education is necessarily the same in each country. In addition, as this indicator does not directly take into account the effects of repetition, it is not strictly comparable between countries with automatic promotion and those allowing grade repetition. It should also be noted that, depending on countries, the enrolment data do not account for many types of continuing education and training. For these reasons, this indicator should be interpreted in the light of complementary indicators, particularly percentage of repeaters.