All I can add to this is that you've gotten some very sound advice and it would be in both your and your friend's interest to heed that advice. Maybe your school doesn't have counsellors that would be able to cope without judging your friend, some schools have terrific counsellors, others not so great.
Could you speak to your own doctor about your friend and ask him to set up an appointment with a professional that could help? Of course you should speak to your friend about this and ask him to please accompany you . Beg if you have to but like Pomtzu mentioned this is way above you, please don't wait for something tragic to happen.
Your friend is right - bi-polar does tend to run in families, the sooner your friend gets help the better.