This paper examines whether the peer-review process of the North Central Association (NCA) is reliable and valid. Reliance on peer judgments has been a part of NCA accreditation, but confidence in the use of peer decisions to certify a school's readiness to implement the improvement plan--Outcomes Accreditation (OA)--was weak. The study focused on three questions: Did the peer reviews reflect criteria for OA school improvement or other factors? Did the peer reviewers make accurate judgments even though improvement plans and school characteristics differed? and Can reviewer accuracy be predicted? The study drew on ratings and diagnostic feedback from 245 reviewers involved in OA peer review from 1992 through 1994. Most of the reviewers were school principals. More than 1,500 independent reviews of school-improvement plans were studied. The results indicate that reviewers were most accurate when they acted on well-developed beliefs specifically related to OA activity and then transferred those beliefs to the evaluation of another school's set of improvement goals. A variety of factors influenced individual accuracy, including the individual's engagement, external environmental pressure for school improvement, and opportunities for collaborative professional exchanges. Reviewers applied OA criteria in accurate holistic decisions even when the schools and their improvement plans differed. Contains 14 references. (RJM)