Hi Kathy,
Do contact your local TAG group. You just missed the conference - it was in December with Jan Davidson as a guest speaker - but they offer several events throughout the year. TAG
Texas Gifted is reputed to be a wonderful organization. I think you would find some peers for your child. BTW, my DS also missed the cutoff and is in 3rd gr but could easily have been in 4th but for a few months. It is frustrating. Just keep challenging him best that you can - projects, nurture his passions, a bit of after schooling...
This is a long road and results won't seem obvious (something I keep reminding myself).
Good luck!