I don't think schools that have gifted programs typically require parents to pay for IQ testing. So what do you think causes underidentification of the non-affluent?
In our district, they only test kids with a teacher referral. A MG kid from a non-affluent background might not "look" as gifted as a normal-bright kid from an affluent background. Not getting enough food or sleep, having a lot of life stress, having to work to support the family, being responsible for younger siblings, not being exposed to educational resources - all those things are more common in less-affluent households, and can mask giftedness.
