He did learn to read, yes.
I read 'Educating Dexter' and he said his biggest achievement was reading the book himself on it's publication.
I saw the Montel show a few years ago when darryl Grant was on with him and they tried to tackle his drug problems. It is such a shame, Dexter always played a big smile on his face and him pumping up the crowd at RFK is my abiding memory from being a 12 year old getting started with this 'weird' game.