I'd probably go with a statement that went something like: "My DC has a learning style and processing profile that makes the average classroom a really poor fit, and X school has a program that we hope will better meet her needs." You might even add "Y professional indicated that this placement would help prevent some likely pitfalls further on." You can enthusiastically agree that you firmly believe that all children should be taught at a pace and depth that challenges and engages them without overwhelming or frustrating them - including your child. You might talk about how lucky parent or friend Z must feel having a child who fits in well in a regular class, has lots of peers who share similar interests, and for whom a straightforward traditional educational path works.
The dark side of an egalitarianism that preaches treating everyone the same is that it ignores the very real diversity of human beings and denies individual uniqueness. My husband is 6'4", muscular, and over 200 lbs. I'm 5' 3" on a tall day and less than half his weight. Give us each 2100 calories a day and I'd get fat, if I didn't throw up from overeating, while he would faint from hunger and waste away. Our meals would be the same, but it would hardly be fair. Your child happens to have a high intellectual "metabolic rate". Withholding "mental food" from such a child would be harmful, but it doesn't necessarily follow that giving the same amount of "mental food" to a child who can't digest it would be beneficial. Treating everyone fairly means treating everyone as an individual and meeting their needs as they are, not as you'd like them to be.
