In your shoes I would choose private behavior therapy (ABA, CBT) and really work on problem behaviors as intensively as can be managed. Giftedness, in our experience, doesn't go away, but problem behaviors stay until they're resolved. You could choose to remediate the problem behaviors now, negotiating the best academic content you can for the moment but prioritizing good social functioning, and get him back into the gifted program again once he's operating in a more socially acceptable way.
DeeDee
I'm interested to explore these private behavior therapy. Where can I get more information about these? I Googled but nothing much came up. I will be visiting the Special School to find out how they can cater to DS. I'm also thinking of homeschooling and sending him for these therapies in the afternoons, instead of sending him to a Special School full-time. Can it work like that?
It does not matter if he gets back on the gifted program once I pull him out. It is an elementary school, and there're just two years left. He is not really engaged in the program, so the only reason I want to hold on to the place is because he has a few very good friends and he treasures those friendships. I asked the school if they would allow him to go back for just a few classes a week to keep the link, but they do not look keen.
One high school did offer him a place to do Grade 9 in the school, but he is not interested at all. He said he'd be the only one who has not broken his voice. So I didn't pursue.