On the basis of the existing research and available theories this paper attempts to determine whether there is any causative relation between the educational reform introduced in Poland in 1999 and the improvement of Polish pupils’ scores in the PISA study. Analysis suggests that the element of the reformsmost likely to have contributed to the improvement of Poland’s PISAscores was the introduction of externally evaluated examinations with a multiple-choice format. There are also two strong methodological conclusions that can be drawn from this research: (1) given the complexity of the reform, its aims and outcomes should be ‘decomposed’ for more detailed analysis, and (2) given the cumulative outcomes of the reform, PISA scores between 2000 and 2012 should be explained by a different set of hypotheses for each round.