I am living in the Balkans for the last four years and my personal experience is that kids here are generally quiet. Very similar to Western Europe. (Zagreb - Croatia, Belgrade and Novi Sad - Serbia).

Before coming here I visited and lived in many European countries and Italians for sure are the loudest in public settings (restaurants for example) - especially when there are many of them together. From my experience from Greek Islands Englishmen are the loudest of all - at home in England they are quiet and polite though . Germans are the quietest ones when traveling to other countries but loud at home sometimes.

All this is totally my subjective point of view of course.