In judging any education system, you need to look at its provision for everyone- the advantaged and the disadvantaged; rural and urban; all ethnic minorities; all SEN and none - not just the absolute standard attained by the elite.
The PISA international comparison, for example, is fundamentally flawed because it allows countries to be selective in who takes the tests.
Equally, judging the German system by an encounter with some able students in Berlin is flawed if it does not balance this with students, perhaps from refugee or Roma families, who have perhaps attended the ‘lower tier’ schools in economically deprived areas of Germany with selective schools. Equally, balance Russian education of wealthy families in Leningrad or Moscow with the experience of families from oppressed minorities deep in the Eastern rural regions.