Dead Connection by Charlie Price
The kids at school think Murray's a loser who has no friends. But it's not true; he does have friends, but they're all dead. You see, Murray spends most of his free time talking to the dead kids at the local cemetery. Hey, the dead need friends too!  Murray thinks his life is pretty routine (well except for talking to dead people) until the caretaker’s daughter at the cemetery starts pestering him; plus he begins to hear a new voice...of a girl who must have recently died. The voice sounds like its in agony. Murray wants to help her, like he helps the others, but he's afraid to speak to her, afraid of experiencing her pain. One of the local police officers thinks Murray's behavior is odd and begins keeping an eye on him. In fact the police might just suspect Murray of being responsible for a local girl's recent disappearance.

On the website for Dead Connection, you can meet the characters and read an excerpt.