Thank you so much for your reply - this really has given me much to think about.
I am going to ask for the block design no time bonus process score and see if that is a factor.
I also think that you have pointed to a very possible explanation for his decreased scores as well as his disengagement. He is a very hands-on kid and when he doesn't "buy into" something he won't engage. He wants to be an entrepreneur and has stated that school subjects are irrelevant. He wants to start up his own business. Perhaps this gifted program is not the best match for him and he would do better in something that he connects to the "real world". However, I worry about him completing school so he has an opportunity to take more "interesting" courses. Without the marks he will not get into post-secondary school. He is finishing grade 10 and will not be getting all of his credits which he is not particularly concerned about.