I don't agree she made a mistake, but stated the idealism of the principle. Why is education in the modern world free or largely free to all? Because it's perhaps the one great leveler: it facilitates opportunity - the individual must still do the work - so a pauper MAY become a president or professor to benefit society. Nowhere is it said opportunity guarantees outcome and she doesn't imply it. Individual traits, some social or inherited, prevent people achieving satisfactory 'outcomes' (what's that really; you can't apply middle-class aspirations to everyone). Some are limited by personal, eg mental or behavioural, or social, eg gross poverty, limitations that prevents them achieving what society deems 'acceptable'. NB our definition of acceptable is informed by social constructs and prejudices. It's clear Teresa meant innate qualities ('born equal'), NOT those achieved through social and constitutional equal opportunity principles. Do we give up just because it's hard?