T.C.
These tests are very difficult. As one poster states you have to pass all subtests. I've been in education for 23 years and have seen just a few kids ever pass this test and skip a grade.
Please consider giving your child an extra year. Most school districts such as Plano, Carrollton, Lewisville etc... offer G/T programs. Your child will be challenged in the regular classroom as long as you are in a quality school district. The math program, in the State of Texas alone, is challenging this year for most children and for that matter the parents. It is not your typical rote math. It requires the kids to dig deeper into their understandings of the problems. It is a powerful approach to teaching children and I think it will better prepare our children for the future.
If you are in the Dallas area...suburb wise... you will find the schools for the most part to be very strong and meet the needs of the children. I can tell you in the last 3 schools I have worked in we have required all of our teachers to get G/T certification just for these reasons. Even if your child doesn't qualify for G/T the teachers can still challenge and meet the students at their ability level.
On a personal level...
My son is a first grade student who received an extra year of kinder due to his birthday. I did private kinder in an accredited school and then public kinder. He is doing quite well in first grade. I'd rather he be successful and challenged in an age appropriate classroom than to be one of the youngest and potentially at the bottom as far as academics. He is doing very well in all academic areas and is challenged daily by his classroom teacher. She knows how to meet the needs of her students and I back her up doing enriching activities with him at home. He is one happy kid and I persoanlly feel this is crucial to his well being and future in the academic world.
Hope this helps some. Good luck with whatever route you decide to go with. Do contact the school counselor. They can provide you with detailed information about the expectations of this test.