This paper presents a model for designing computer-based simulation environments within a constructivist framework for the K-12 school setting. The following primary criteria for the development of simulations are proposed: (1) the problem needs to be authentic; (2) the cognitive demand in learning should be authentic; (3) scaffolding supports a focused effort relevant to the learning goals; (4) coaching promotes learning rather than directing or correcting performance; (5) reflection supports abstracting, synthesizing, and extending the learning; and (6) the environment should be engaging. With these criteria as a basis, this paper evaluates "The Chelsea Bank," a simulation package that consists of 15 scenarios in which groups of learners act as either a bank teller or a customer service representative. Contains 12 references. (AEF)