This document consists of seven chapters. The first chapter analyzes the modeling process and gives reasons for introducing a modeling approach in classrooms, arguing that students will develop more confident and positive attitudes toward mathematics. The next five chapters contain case studies, which focus, respectively on: whether it is more economical to rent or buy a television set; how pricing policy affects profit; how a rear window wiper should be positioned on an automobile to sweep the maximum area; the mathematics of the long jump; and which of three schools should be shut due to declining enrollments (by calculating traveling time by different modes of transportation). Each of these chapters includes: an introduction to the problem to be modeled, with prerequisites and the target age-range (and learning objectives, when applicable); list of assumptions on which the model is based; an influence diagram showing the relationship between factors; model development (which may consist of several parts); and a concluding section which draws out implications and gives ideas for further work. Assessment items are included for several models. The final chapter contains a list of models which could be used in the classroom together with a list of references and a bibliography. (JN)