It actually depends a lot on where you live and the specific context of your school. It's not like it's a uniform phenomenon across all of Italy - in some areas, especially in the South and in smaller towns, communion is still very widespread and almost a social norm. In other areas, particularly in northern cities and in more secular environments, the number of kids who do it has actually dropped compared to a generation ago.
What's mainly changed is that today there's no longer that automatic social pressure from before. Back then you did it because "that's what you do", all your classmates did it, and refusing was almost unthinkable. Now parents have fewer cultural and religious constraints, and they decide more freely whether to have their kids do it or not. Plus, non-believing families or those with a weaker faith feel less obligated to follow the tradition just to not be left out of the group.
If hardly anyone in your son's class has done it, you're probably in an area where this secularization trend is more advanced. It doesn't mean it's a problem - it's just that Italian society is becoming more plural from a religious and cultural point of view. Before, religiosity was more homogeneous, now it isn't.