I understand your situation, I also attend a private school, and the teachers know more about the students than they should know....
Here's my advice
The guy is 2 years younger than you, but he's probably as grown up as you, so there's no problem there. The phone number you'll eventually get it. The real problem could be with your friend. Wait 'till things cool down, then talk to her calmly. Tell her how you feel, maybe it will take her time to understand but as long as you talk to her honestly, she'll come to her senses. One more tip, it would really help if you found some guy that is interested on your friend, and that she is int interested on him, That way it could be less tense.