indigo is correct: the NNAT (presumably the 2nd edition, at that time) is most similar to the nonverbal portion of the CogAT. Interesting that they chose to give a six-year-old first grader level 8, which is generally intended for eight-year-olds in second or third grade. They must have been expecting a high score. The NNAT standard scores are on the same percentile scaling as other commonly-used cognitive instruments (mean of 100, SD of 15). So yes, 99th %ile.
Grieved that she had the misfortune to encounter a teacher who would tell a child not to read.
With the caveat that both instruments are better regarded as screeners than as comprehensive measures, I will say that your DD does appear to have very strong cognitive gifts, but in an area which is not always fully appreciated by teachers, as it is less frequently tapped for academic learning. In the more school-related areas (quantitative, verbal), those scores would usually be described as optimally gifted. Conceptual/pattern learners like your child sometimes don't have a venue to display their true gifts until later in school or life, when creative problem-solving, abstraction, and integration become much more important than basic skills, knowledge collection, and efficient output.
If there is a specific problem that requires a solution, then it is worth further evaluation. I wouldn't go into an evaluation as either a fishing expedition, or with a specific answer in mind, but if something is interfering with her success and joy in school or in life, then a good evaluation may provide some insight and possible solutions.
