AbstractScores in standardized international student achievement tests and some recent adult literacy studies provide interesting data on the quality of educational outputs and on the skill level of the population that can be a useful complement to the data on the quantity of schooling which have been most commonly used in the growth literature. This paper describes the most recent available primary data on the subject, reviews different attempts to organize, standardize, and summarize them, and discusses the strengths and weaknesses of the existing indicators and their potential usefulness as explanatory variables in empirical analyses of the determinants of income and welfare levels and growth rates. A final section investigates the distribution of these indicators across a sample of 21 OECD countries.