I am sorry but if you can't share your knowledge you really know nothing. Why did I say that?? Knowledge by itself requires some sort of sociality. Whenever you know sth interesting it's just impossible to hold on to it. You would want smn to talk to abt stuffs. It's just the way education works. So not having a desire to share what you know might mean you actually know very little. But it might also be due to the fierce competition created by the school system. In that case just try to intentionally sharw whatever you know to whomever you want. It might work.