Authors	Countries	Empirical Method	Results
Hanushek and Woessmann [14]	World Program for International Student Assessment (PISA) testing math, science, and reading	Least-squares regressions with instrumental variables in quasi-experimental research methods	Class size is a relevant variable only in settings with low teacher quality.
Hanushek and Woessmann [14]			Teachers are more closely related to student outcomes.
Ouédraogo [4]	Burkina Faso	Ordinary least squares (OLS) in the error correction model	Positive effect of student-teacher ratio.
			Short-term negative and long-term positive effect of percentage of qualified teachers.
			Long-term negative effect of overall repetition rate.
			Not significant in the short- and long-term positive effect on the literacy rate.
			Negative effect of unit costs of budgetary public expenditure.
			Positive effect in the short- and long-term total operating expenditure.
			Positive effect of salary unit expenditure.
			Positive effect of unit investment expenditure.
Al-Samarrai [15]	UNESCO countries	OLS	Expenditure per pupil in primary school has a positive significant effect on the survival rate only up to Grade 5 and a negative significant effect on school enrollment rates. The other coefficients are not significant.
Hanushek and Kimko [16]	Countries of the International Association for the Evaluation of Educational Achievement (IEA) and International Assessment of Educational Progress (IAEP)	OLS	Student-teacher ratio is not significant.
			Ordinary spending on education per student has a negative effect.
			Total expenditure on education in percent of GDP has a negative effect.
Wößmann [17]	United States of America, developing countries, OECD countries, East Asian countries	Weighted least squares	International differences in student performance are not caused by differences in schooling resources but are mainly due to differences in educational institutions. Class size has a positive effect.