What are some signs that a young teenage boy may being sexually abused?

Normally when a teenage boy is sexually abused you will never know. That is something that normally gets kept a secret.

Hi sometimes there are no ways of knowing unless you are close to this boy and he tells you or you see bruises on his arms, face, neck or body. The best thing is to call Social Services and involve them. If you do suspect this it is not right to let it continue. Think of what the poor boy is going through. When there is suspicion of this they will investigate further and will get to the bottom of this. It is terrible for a young boy to be sexually abused, mentally there's a lot that goes on and you could be helping prevent this poor child from having mental issues the rest of his life. So do the right thing. Good Luck.

i would at least speak to authorities as THEY can give you some signs to look for.

Not wanting to misreport is a bad excuse for allowing it to continue if it is happening.