Peer Groups in Korea

Due to my status in Japan, as Foreigner, I will rather introduce peer groups in Korea.
In Korea, peer groups usually divided according to what they have interested in. For example, nerds gather up with those kind of nerdy kids. Sports lovers hang out with whom like and play sports. It seems like those group members do not interact, communicate, and hang out together. However, they quite often hang out together though.
Also, teenaged kids mostly divided into groups of boys and girls. If there are some stuff to do with, then they hang out sometimes But, it is very rare to see bunch of boys and girls hanging out.

In my opinion, peer groups in Korea are similar as those of Japan. However based on my experience in states, there are many boys and girls mixed groups in states. The group of mine was also mixed. We have lunch together usually and do homework or projects together. These things are not really common thing in Korea and Japan. Boys stick with boys and vice versa.