This paper describes an evaluation model developed by the Ontario Ministry of Education and illustrates how it was adapted to meet local and provincial needs of the Scarborough School System for accountability data and direction for change. The basic Cooperative Evaluation and Development of School Systems (CEDSS) model includes five stages of evaluation (initiation, internal evaluation, external evaluation, cooperative review, and final evaluation report) and three stages of development (analysis and response, implementation and incorporation). Three features of the school system prompted modification of the basic CEDSS model: (1) its large size; (2) its self-contained Research Centre; and (3) its desire to reflect the wishes of board employees and the public regarding evaluated topics. A provision was made for a Board Advisory Committee to provide input to decision making at various stages, and for an Initiation Team to assist in effecting system and community awareness and in eliciting a willingness to participate in CEDSS. The customary one-year timeline for a CEDSS project was extended to two years in Scarborough. A list of concerns for the evaluation phase of future CEDSS projects is presented. The benefits of this project both to the Ministry of Education and to the local school system are briefly described. (PN)