"Slightly" or "mildly" gifted kids make the cut-off to get gifted services in most areas where they're offered, but they don't get the highest scores in the district, unless the district is very small. You might be underestimating your DS. It might be worth your time to review his test scores and see where they really place him.
Your absolutely right, I very well might be underestimating him. Only time will tell. I always knew he was bright and honestly it wasn't a huge surprise when he passed his G/T testing with very high marks. His scores on the NWEA reading and math were a 99 and 98 and I was told one of the highest in his age level. But I'm guessing he's only mildly gifted due to what I read that most children of higher level giftedness perform. But yes, he actually met the districts standards of "gifted" near the top of the charts and has been invited to attend the G/T public school. I just hope he likes it and doesn't feel too pressured by the workload.