Sorry, but I think this is nearly 95% your fault. Yes, he was stupid in the fact that he just chilled in the street. But you clearly saw him there. You should have gone way behind him if he was slowing down.

Its like seeing a biker in front of you slow down, and you do the same. Then, you continue becuase you assume he's done braking..... And he's not.....

Also, filing a police report is a bit extreme. So what, you crashed. Would complain to you city council if you hit a light post? Plus, that kid could have got equally pissed at you for crashing into him since skateboarders DO have the right of way.