This is the first in a series of articles that address the use of educational indicators to inform policy. The aim of the series is to provide an in-depth discussion of a single indicator or set of educational indicators from a data-user perspective. Each article will present the most recent cross-national comparisons and provide practical examples of interpreting an indicator for benchmarking systems, assessing policies and for measuring progress towards international development goals. They will also address the specific advantages of a particular measure, its limitations and its links to other indicators. This series focuses primarily on the interpretation and use of indicators rather than providing technical documentation about how indicators are calculated. This first article looks at a measure of the volume of educational outputs: the school life-expectancy indicator. (Contains 3 figures and 1 note.)