A few thoughts came to mind as I read your post.
- You earlier mentioned that he had not memorized his multiplication tables. Have you worked with him at home to support his learning?
- - If he is visual, you could help him "see" and "picture" the multiplication.
- - If he is auditory, there are songs for multiplication, that once memorized may easily come to mind when he needs to recite multiplication tables.
- - As an alternative, there is always classic "drill," the no-fun, timed tests from years gone by.
Drill sheets can now be found online.
- If you believe your child may need or benefit from tests for learning disabilities or dyspraxia, you may want to focus on arranging for that, prior to changing schools.
- Are classes in his areas of interest and ability currently available from Northwestern CTD and/or JHU CTY?
- Are you able to home school?
- Regarding being bullied and an outcast - - Are you able to invite any child(ren) over to play, or plan a meet-up with one or more families at a local spot such as a pizza place, museum, zoo, or park? Are there any other groups of children he could meet (city recreation department, sports team, volunteer activity at pet shelter, church, etc)