My younger brother has changed so much since last few months. I can't find reason for this and I want (he) to be a better person than he is now. Any advice？

He is in Grade 11 now. Till Grade 10, he was in a common school. For his better education we changed his school to a better one in this city, but he had lots of (friendly) in his old school. So he didn't want us to change his school, but we still did.

It has been five months he came to the new school. And we've started noticing some bad changes. He has become very (polite) to our parents and me. He used to (do) well in studies till Grade 10, but now he starts failing in his subjects and he (enjoy) playing computer games. This habit of his took up most of his time and began to influence his schoolwork. So our parents don't allow him to play games

Once he had a parent-teacher meeting his school but he didn't tell us about it. Later, we asked the reason, he just said he forgot to tell. And when we looked up his (result) of his monthly school tests, we found he failed in two of five of his subjects. He often complains(抱怨) of headaches in one half of his head and doesn't go to school. We asked several doctors and after having a (little) tests, doctors found nothing.

What should we do? Any advice is welcome.