Translation:He is not an adult, he is sixteen years old.
I was interested in your question so did some research on-line. The following is not authoritative but is what I found:
Age of legal majority is 21. Age of consent is generally 14 years, but those aged 13 may engage with partners who are less than 3 years older. It rises to 16 if there is some sort of influence from one party eg teacher, priest etc. Marriageable age is 18 but courts may allow 16. Legal alcohol consumption is mostly age 16 but in some areas 18. Driving age 18 but may be accompanied at 17 if properly authorized. Voting age is 18 but for the Senate it is 25.
Typically rather complicated ;)
Typical, yes :) I managed to shock a Spanish friend of mine listing all the grading systems in the Italian school: in primary school I was graded with verbose marks on a 1 to 10 scale (e.g. sufficiente = 6, discreto = 7, and so on), in middle school with an English-style letter system from F to A, in high school with a numeric 1 to 10, in university 1 to 30 plus 33, in the final degree 1 to 110 plus "cum laude". I wonder how it is now, every new education minister is bound to change something, as a sport.
Off-topic aside, the general coming-of-age is considered to be at 18 :)
I am neither italian nor english native speaker. Sometimes I still struggle with my English, although I've been learning it for decades now. Just out of curiosity, is it really bad English to say "...he has sixteen years" in place of "...he is sixteen years old"? Tnx in advance!
It is not bad English; it just has a different meaning. "He is sixteen years old," deals with age. "He has sixteen years," sounds like a deadline. "He has sixteen years...to get a new roof for his house," for example. "He has sixteen years to pay the bank back," is another example; but "has" is never used for age.