A center is a “three dimensional lesson plan.” Each center contains menus with set-up procedures, directions and lists of materials and tools. Resources include images by student and adult artists, books, charts and other related references. Materials and tools are organized for easy access and return. Centers can be as large as half the room or as small as a shoe box and can be arranged to accomodate a wide variety of ages and abilities. Some basic centers will remain in the classroom all year, while others make brief, limited appearances. Centers are opened one at a time, as students show their teacher that they are ready to handle more choices.