We examine if the OECD survey of adult skills, PIAAC, can provide information about the relative quality of education and training in Denmark, Finland, Norway and Sweden. We find that the average population scores are inappropriate while the mean scores of natives well approximate the skills of individuals that had the chance to attend the countries' education and training systems in full. Native mean scores are invariably higher than population scores in all four countries, for all skills: literacy, numeracy, and ICT problem-solving. Thus, viewed as quality measures, average population scores are biased downwards. The native-population differences are small -- at most 3.5% of population scores -- but statistically significant. We also consider how the ranks of these Nordic countries in the international skill distribution are changed when mean native scores are substituted for average population scores. Except for an improvement in Sweden's numeracy rank, all changes are statistically insignificant.