'Cured' is such an inappropriate word. These are not illnesses, but a natural part of human diversity.
   What can be done is to teach behaviours which are appropriate to culturally normative institutions. An alternative is not to expose them to these ratyher artificial institutions.This altrnative is normally the reserve of those who have 'independent means.'
In the 1909 edition of the 'handbook of mental deficiency' Tredgold and Soddy noted that a fair proportion of the feeble minded were members of the gentry 'well suited to the amusements of their class', and therefore in no need of socital intervention.King George V's eldest son had 'learning difficulties' but was provided with a secluded cottage, servants etc. No need to cure the rich!