Paramount to the Boy who tells is immediate support of his decision.
Disclosure of Sexual Conduct is shaming. He is violating secrets, and agreements the abuser has put in place to silence him. Disclosure of victimization places him in awareness of his powerlessness. Disclosure of his shame and anguish includes self awareness and pain. Understand that the truth is so horrible that dissociation is common, lies are common, denial is common, and self harm is common. A Goth teen who presents with cutting mutilation in response to sexual victimization isn't cutting because they were victimized, the reality of their internal processes is such that they respond with self harm to shame. Similarly the boy will experience self disgust, anger at powerlessness, pain and loss of self esteem. Protect him, not by punishing the abuser, but by lifting up his decision to tell. Explain that shame has no place in this. Explain that the abuser was the one responsible for the abuse. Check for his understanding of self worth and empower him to rise above his abuse.
Damage from CSA is not linear nor static. Two boys who suffer the exact same circumstances in CSA have different degrees of damage based on how they view their CSA. Internally tortured boys don't often know who to turn to or how. Make sure that they understand they are believed, loved, cared for, and protected.
They must be affirmed for telling. They must be shown that telling was the right thing to do. They must have appropriate responses to the abuse modeled so they know how to feel and how to act about their abuse. They will also need some counseling. But PARAMOUNT, make sure they know they were Right to tell.
Re-affirm the identity and worth of the boy. Model appropriate responses to the situation on his part and on your part. Explain that to feel bad about it is normal and not uncommon. Damage incurred from sexual abuse is not static nor is it linear. Many of the children will sustain more and more damage as they deal with the reality of their abuse. As they age they will not be immune. Many of them revisit the shameful secrets of their past as they mature. Dealing with ongoing trauma as it comes up and continuing to affirm them and their worth reinforces their correct action in disclosure.
Protect them from the abuser immediately. Protect them from incorrect assumptions about their worth immediately. Validate them NOW. They need to know that their voice counted.
I was silenced by my abuser. I was silenced by my family too. I was told not to talk about it because no one wanted to hear about it. I was taught to be ashamed of it and that it was my fault.