As with most research, take multiple sources. A quick survey showed this (admittedly rather old paper), but it does show the immediate effect:
https://www.jstor.org/stable/pdf/146368.pdf?seq=1#page_scan_...
>On average over the post-ADA period, employment of men with disabilities was 7.2 percentage points lower than before the act was passed. In addition, wages of disabled men did not change with the passage of the ADA.
http://www.law.harvard.edu/programs/olin_center/papers/pdf/J...
This one is long, and they do mention some positive impact on education later. Didn't read that far though.
>while relative disabled employment declined significantly just after the ADA’s enactment in states in which these provisions were a substantial innovation relative to the pre-ADA state-level employment discrimination regime, relative disabled employment was stable in states with ADA-like employment discrimination regimes in place prior to the ADA’s enactment
Non-exhaustive search, but the data seems to indicate that ADA reduced employment for the disabled shortly after inception. I'm not certain on the longer term effects (those are also much more annoying to model here).
