I think that his science is impressive, and you may want to do a portfolio, but I wouldn't stress the Math, as by age would be actually be a 3rd grader in some states, so doing 5th grade is definitly MG, but not a sign of PG.
Have him dictate some book reports of some of his harder books, and video him talking about his HS Science, and I think you have a shot at DYS.
I thought that the portfolio option was for kids who hadn't been tested for financial or other reasons, not kids with test scores that didn't qualify. No?
On the original question, though, I too wouldn't assume that he isn't gifted, although he may not be DYS level gifted. My oldest had a 132 IQ on the WISC-IV at 7, which would indicate a moderately gifted child. She consistently performs like a HG+ type of kid although I don't have any indication that she is DYS eligible either. She's had a few scores on the cusp of DYS eligibility, but overall has not had anything that absolutely says she would qualify. We aren't pursuing DYS for her for that reason.
Like others have said, it is a snapshot of one day and some kids don't test as well as others.
