The Collaborative International Dictionary of English v.0.48:

Coeducation \Co*ed`u*ca"tion\ (?; 135), n.
   An educating together, of different sexes or races; -- now
   used almost exclusively in reference to the education males
   and females together.
   [WordNet 1.5 +PJC] -- Co*ed`u*ca"tion*al, a.
   [1913 Webster]

WordNet (r) 3.0 (2006):

coeducational
    adj 1: attended by members of both sexes [syn: co-ed,
           coeducational]

Moby Thesaurus II by Grady Ward, 1.0:

24 Moby Thesaurus words for "coeducational":
   autodidactic, cultural, didactic, disciplinary, edifying,
   educating, educational, educative, enlightening, exhortatory,
   homiletic, hortatory, illuminating, informative, initiatory,
   instructive, introductory, lecturing, preaching, preceptive,
   propaedeutic, self-teaching, teaching, tuitionary