Flaming arrow......now thats funny  

Patience is a virtue. Carbon arrows on your balcony is a real test! Handle w/care.., but handle it! You'll do fine.

Do not wait for an accident to happen, it's too late then. Just think how you would feel for not doing/saying anything. That bow is not a toy.

Say something, in a diplomatic way to the mother.
Have it down that you have made the mother aware.
The next time, should something happen again, she will say you should have let her know.
You or your kidsmay not have another chance.

I agree, dont rat the Kid out to his Momma! Sounds like he gets enough Guff as it is. Take him aside and explain to him WHY you arent going to tell, then explain to him as best you can that You are willing to Work with him, with his Parents Permission of course, be a Mentor to the poor boy since it doesnt sound like his Dad is stepping up to it.
  You may have just saved Your Kids AND him too!! They ALL Gotta Learn, I agree, at least it wasnt in your Roof, or Worse for sure. If he is a Good Kid and will take Your Explaination about Your Concerns about You, Your Wife, and Your Kids getting arrowed by His Mistake, he just may never do it again anyway.  
   That is a Tough One. Gotta get 'em FAST!! before he does something he will Regret for Life!!

In my opinion this is not an archery question to be discussed here; it is a moral obligation question that presents its self. You sir, by virtue of shooting a bow should know it is a Weapon, not to be played with or to shoot at others, but must be respected. By virture of your handling so far you have let your obligation to your family,other neighbors,kids parents, and the community go by the wayside.Have you ever thought of why his parents are so strict, maybe they know something you don't, how would you feel if someone does get shot. Do you know this could come back on you at some time down the line.I,ve never put myself in this situation but know others, who gave the poor kid a break,who were called out after something of a serious nature happened. I'm sorry to be so annoyed about this thread but believe that we all have to help take care of our communities and help to protect others even to the extent of being a bad guy. Do what you know needs to be done,your not a rat but someone concerned!! Worry about being a "mentor" later!

You found a projectile on the deck where your kids walk around.  I think you have to do something.  You don't want to be trying to do something after that arrow is sticking out of your child's arm.

Talking to the boy is where I would start.  Basic safety stuff.  We've all been dumb, the key here is him not staying dumb.  Offer to teach him, too.  If mom wants to be a jerk about it, that's her shortcoming, not yours.

Do the right thing.  Don't worry about whether others will do the right thing.

is she hot? is she single?  lol... but really, a mentor would be the greatest gift this kid could use.

I feel that the mom has to be informed. If something like this happened again and somebody got hurt, she could be held liable. You still should offer to help him learn proper archery technique and safety, but it needs to be Mama's call. Not bringing it to her attention leaves you somewhat negligent. I don't consider it to be ratting out the kid, but, rather, its a matter of safety over all else.

If my son shot an arrow into my neighbor's house, I would expect my neighbor to let me know. I would also expect my son to tell me that my neighbor would like to see me.

A new "secret" friend who was an adult male would creep me out!  

The arrow on the desk already "ratted out" this kid.

I think you have to let this kid know somehow   that arrows are deadly and you cant have deadly arrows landing on the neighbors deck. I'd try to let him know personally.

"Secret Friend"? Where did THAT Paranoid Idea come from? Egads. If You are referring to My Post, READ the Whole Post Please.

Kids make mistakes. We all know that, but as a parent I would want to know if my kids had done something like this. I wouldn't be able to handle the guilt of knowing I might have been able to prevent someone being hurt. The boys mother has a right to know because she is responsible for her child's actions and could be held accountable if another accident happened. That is just my opinion of how to handle it. Maybe after talking to her you could still offer to give her son some pointers if she is willing. Good luck with a tough situation.