SOCIAL Anxiety. Yesterday consulted me!

My brother suffers from Social anxiety from last 5-8 years.His academics performance have degraded heavily from the last 2-3 years.He yesterday consulted me regarding the issues that he is facing and the reason why he is not performing good.He told me that he feels really uncomfortable in front of people and always feel that he is being judged.He feels that he is making everyone bored.He told me that it started when people around him started making fun of him as he was not able to speak properly in front of his friends in school bus,he started avoiding every social activity.When he comes to home in vactions,he rarely conversate with me or any other family members.We thought that he is highly introvert but this was not the case.He use to study day n night but his performance in exams where almost at the bottom.We have never forced him for studying or any other stuff.He says that he also dont want to socialize with family members.He also dont have an account on any social networking site