I would not over-worry or over-think this decision either way - if you think he'd benefit from switching to gifted math, I'd advocate for it, but otoh if you think he's happy and ok for this year where he's at, I'd let him stay. My thinking is a bit round-about and may include things others wouldn't think of based on a potential 2e situation with your ds - so here goes, in no particular order:

1) If you *do* decide to advocate to get him into the gifted math pull-out, I'd take a second-look at the questions he's missed in previous testing. If he *is* dysgraphic or dyslexic, there's a chance he might be missing math problems simply due to copying numbers incorrectly or switching them around accidentally etc. That happened to my dysgraphic ds *all* the time in elementary school math. My dyslexic dd also misses math word problems not because she doesn't understand the math conceptually but because she doesn't interpret what she's read correctly - if you listen to her talk through a word problem it's clear she's not read the actual words correctly but she is doing the correct math for what she thought she read.

2) Since there's the possibility of dyslexia/dysgraphia, my main focus at this point would be on the further testing you need to determine what's up, and then focus on remediation and putting accommodations in place. Then your ds will be ready *fully* to enter higher-level gifted or accelerated programs and will be able to be successful at them. I wouldn't want to place him in an accelerated program if there was any concern that he might struggle or not do well there due to an LD.

3) I wouldn't worry about whether or not math was a favorite subject for my child as a requirement for accelerating him in math. You might be surprised to find that once he's accelerated and challenged math actually becomes his favorite subject, or he might never ever like math at all - but neither one of those is a reason to accelerate/not accelerate. Would you hold your ds back a year if the school asked you to just because he hadn't shown enthusiasm about moving forward to the next grade?

Hope that makes sense - good luck with your advocating!

polarbear