Should the NAACP have challenged the earlier Plessy decision instead of waiting to appeal the Brown decision? Could things have moved forward more quickly if they had?
I personally don't think it would have significantly helped the Civil Rights cause if the NAACP had challenged the Plessy decision. Arguing for a person who was 7/8 Caucasian who was forced to sit in a black rail car in a deeply segregated state wouldn't have had the same emotional impact as defending a small child's right to attend a nearby school in Kansas.
http://caselaw.lp.findlaw.com/scripts/getcase.pl?navby=case&court=US&vol=163&page=537
http://www.yale.edu/ynhti/curriculum/units/1982/3/82.03.06.x.html