HABO: when did "special" become a synonym for intellectual disability?

i think this is a Gen X thing, i can't seem to come up with the right search terms to trace the origin/timing.

my memory is that there was an organized effort to replace the use of "mentally retarded" with "special", which had the unintended result of kids calling someone "special" as a pejorative where they used to use the R-slur.

i am a bad person and had a solid laugh over Trump calling the rioters "very special" yesterday.