The Naglieri Ability Index (NAI) compares your child to the other students of the same age taking the test. Most students fall between 90 and 110. An NAI of 136 is at the top end of the NAI scale and is "Very Superior," the highest qualitative description available.
Your child's NNAT assessment report gives her percentile rank compared to others her age. An NAI of 136 places your child in the 99th percentile which means she scored as well as or higher than 99 percent of the other children her age that took the test.
Mensa is an organization whose members score in the top 2 percent of the population on standardized intelligence tests (such as the NNAT). American Mensa accepts members who have a score of 130 or higher on the NNAT. A score of 136 qualifies your child for membership in an organization whose members, according to American Mensa, share high intelligence.