Has he had an evaluation for attention deficit disorder? That's probably where I would start. It sounds like his verbal score probably isn't really accurate if he was that distracted.
My DD has ADHD and is also very slow with getting written work done. Her verbal and non-verbal scores were both above the 99th percentile but her processing speed score was something like the 33rd percentile. She was medicated when she took the test, otherwise she probably wouldn't have scored so high in the other sections.
