Comparing outcomes of existing systems would be good, assuming that you have multiple systems used by the same population. Some countries have this data, other countries don’t. For example, if majority of schools in a country follows a government blueprint, and only a few alternative schools are allowed to coexist, it is not obvious whether the differences between their results are caused by different education, or simply by a selection bias (alternative schools are chosen by parents who are more interested in their child’s education).
If one is trying to improve the public education system in one country, one can compare it to the public systems in other countries, which will take in a broad swathe of the population.
If one is trying to improve the public education system in one country, one can compare it to the public systems in other countries, which will take in a broad swathe of the population.