A family is racist, and the parents think one of their children is an idiot, but then the presumed idiot child and one of their siblings start learning a form of sign language from the people they are racist against?

I originally pictured a white family, with deaf child and a hearing child who start learning Plains Indian Sign Language from Native American’s, in 18th century United States. Another possibility would be a white family, with a non-verbal autistic child and a neurotypical child learning Black American Sign Language from a black family, in 20th century United States. Is there any book with a premise like this. It can be set in any country, as long was it is available in English, and in any time period.

by neigh102