On the so-called 'Pisa' tests, comparing achievement in various countries:

The OECD has set its face against measuring achievement in relation to the curriculum, preferring to try to capture "literacy" or "the ability to use knowledge and skills to meet real-life challenges".

In practice, this has led to wordy questions dealing with elementary or commonsense concepts. A study in Ireland found that 15-year-olds not taking science did as well in the science test as those who were.