I understand- this is tricky. My girls are still young, but I have worked in schools. How close is your friend? We are all glad you came to us, but-What is your hesitation? Do you know why? Has the subject of teen sex come up in conversations?
There is a chance that the teen was just lying to be cool in front of "friends".
How much unsupervised time does this teen have?
How much time does your teen spend with this teen? Are they girls or boys? Good friends?
If the deed is fact- there is nothing that can be done about it- except to prevent it from happening in the future.
So, just to be on the safe side.
Talk to the school counselor about programs they have.
The teen will most likely deny deny deny if confronted.
If you tell the parents and they talk to teen there will definitely be a backlash- your child could really get into some trouble- kids can be really mean when they find that someone ratted them out. So , be aware. As my husband says: No good deed goes unpunished. There is even a chance that the parents will not appreciate your butting in- and you loose a chance to help this child indirectly.
Maybe you could offer to have outings and sleepovers - or other appropriate activities to lessen the risk of this child being unsupervised. Find some new and old movies- Invite all your teen's friends. Lame? Maybe. Then again, everything to them is lame ...at least at first. Get lots of good treats- they will come. Be a little involved and available- It is good to have your house to be the place to go- you know who is supervising your kid- and you get to know their friends.
How much of a friend is this teen to your child? Can she/he have an influence? Can he/she find out or educate this teen about physical protection and emotional consequences.
Are you or your friends practicing Christians? Ask your spiritual counselor.
What if someone came to you with this information about your daughter/son? The first emotions you would probably feel would be fear shame hurt and anger.
No matter how close you are to your child - it is unlikely they will tell you when they become sexually involved.
Boy- I am not looking forward to this for myself.
Many prayers and Good luck-