Perhaps your son's passions really do exist - just under wraps?
I hope so.
We've struggled all year to increase Miss 8's care-factor with school work. The grade skip certainly helped a little, but I'm hoping that care will come with age too. Finding the right art teacher, music teacher, school teacher is critical, but it doesn't solve everything - just another part of the puzzle. Good luck solving yours... jojo
His grade skip seemed to help a little, as well, but we're noticing that he's slowly starting to slack off again. This is one of the many reasons why we're planning to homeschool next year - to allow him to move at a pace that's good for him in the hopes that we'll see more of his interests/motivations.
My DS8 is similar. One method I have found to get him interested in something is to use the good ole Tom Sawyer trick. I will start doing *whatever* and get totally into it without saying anything. Sooner rather than later the kids want to know what Mom is up to and then they want to try but I say "Noooooooo, hmmmmmmmm not right now I am really getting into this." Then they REALLY want to try. "Mom, come on, you had a turn let us try!" And I say "Give me a minute. I'm not done." By this point I could be deboning chicken for gosh sake and they would want desperately to try it.
I have used this to interest them in certain books, educational software, puzzles, games, workbooks etc.
Note: To keep them interested is trickier and I will often check in with them to ask questions and show my continued interest or I will challenge them if it is a game etc.

We've had almost the exact same conversations, LOL.
Perhaps he just hasn't discovered what makes him go yet. Or maybe he has and I haven't seen it. I can't wait for next year! Thank you all.