While large-scale education assessments, such as the PISA, are meant to show how education systems are faring around the world, evidence shows these assessments come with a host of problems.
Big education tests can distort the definition of quality education. For example, high PISA-scoring educational systems, such as Singapore, Finland, Korea and Shanghai, are viewed as high-quality systems. But we think the quality of education is much more than any education test can assess.

Source: The Conversation