The education ministry's draft plans for a new privately managed exam in fiscal 2020 or partially maintaining the current government-backed exam until fiscal 2023 for university admissions will likely provoke a heated debate. But in the final analysis, it will make little difference because of the limitations of all standardized tests.

The purpose of administering either standardized exam is to be able to help universities rank students. If test designers loaded up their instruments with questions measuring the most important content effectively taught in high schools, scores would in most cases be clumped closely together. That would make comparisons hard to achieve.

To avoid that possibility, test designers aim to engineer score spread. There's nothing sinister about this practice. It's how all standardized tests are designed by necessity. The SAT, which is as close to a university admissions test as those used in Japan, has long done this. The SAT achieves this goal by including many questions that reflect the socio-economic backgrounds of students, since doing so has long produced the desired outcome.