I see you are getting many helpful comments here, and I am sure you will receive more. I just wanted to give my .02 -- don't feel bad, you have not failed your child. We all do our best. I virtually ignored my HG++ (EG? PG?) middle child while running a 50 hour a week ABA program in my house for my oldest, who was born with autism. The ABA program went on for 5 years and during that time took most of my attention. Middle child was ignored and his needs were neglected (youngest not born yet). I am sure you are doing your best, so don't beat yourself up.
Second, I don't buy those test results from September. My kids (all three) have tended to be somewhat erratic test takers. Maybe yours is too. Sometimes it seems they go into autopilot when completing tests that are too easy. Maybe they underestimate the effort required, or maybe they can't be bothered? Who knows. My kids shine on above level assessments and have always performed much better and more consistently on those. Maybe your son is the same? Any chance your child can take the SCAT or even the SAT, perhaps through one of the gifted programs (Duke or JHU CTY)? A great result on one of those perhaps could be used to convince the school that your ds belongs in the advanced math group.
If all else fails, you can do EPGY open enrollment math at home (I hope), but if I were you I would try to get some alternative data (do some testing outside school), and try to force the school to place your child in the advanced math program. GL. I'm sure you will get many great suggestions here. Most of all though, do not be too hard on yourself. It will all work out, with the effort you are making, one way or another. BTW, my ds9 would love your kid, and I am sure he would find your son very cool.
