I have a son the same age and exact same problems.  I have tried everything and feel your pain that the school doesn't seem to help and their care for the situation may seem very transparent.

I started my child in therapy and his therapist suggested that we start with small things to help build my childs self esteem.  She said and I quote "he needs to experience some success as soon as possible".  I started him in some sports, and started to really build him up with praise around the house.  It is very very slow coming but I think I'm finally starting to break through.

It's hard when 14 is so awkward, you want to be a friend and a parent, but they seem to kind of take advantage of that.  Best wishes in your efforts, but I'd really think about getting him a mentor or involved in things that will bring him a little success as soon as possible.  Martial arts is always a great motivator, fun, active and disciplined... maybe you could try that???