- Successful education systems are able to guarantee that all students succeed at high levels.
- Across OECD countries, around 60% of the overall, country-level variation in student performance can be traced to differences in how well students who attend the same school can be expected to perform.
- About 40% of the variation in student performance in OECD countries is observed between schools; but among high-performing countries, differences in performance are generally smaller than those in the average OECD country.
