when i was a kiddo, i can remember 5 kids that were ill with various issues. that’s K-12.
now everybody has a relative with something, and autism seems to be #1 on the list.
How??
Mainstreaming for one thing. When we where in school, mentally disabled children went to special schools, stayed home or were surrendered to the state hospital system if they were violent.
We didn’t see them, so we didn’t know they existed.
Also, now practically everything except Down’s is called autism.