My Students' Problems(3)

Now about my students:
Although they were the hosts, they were actually acting as spectators!
They didn’t have enough self-confidence to show their abilities in singing and playing musical instruments although one of them was really a professional player.
Iranian students weren’t active as Korean students too.
Both of these groups were in a same age, but Korean students were more happy than my students.
This was making me crazy!
What kinds of problems had made this behavioral gap between them?

P.S : They couldn’t dance(not traditional , not modern), because it is prohibited in Iranian schools.