In many cases, teachers develop their own curricula, often refining and improving them over years, although it is also common for teachers to adapt lessons and syllabi created by other teachers, use curriculum templates and guides to structure their lessons and courses, or purchase prepackaged curricula from individuals and companies. In some cases, schools purchase comprehensive, multigrade curriculum packages—often in a particular subject area, such as mathematics—that teachers are required to use or follow. Curriculum may also encompass a school’s academic requirements for graduation, such as the courses students have to take and pass, the number of credits students must complete, and other requirements, such as completing a capstone project or a certain number of community-service hours. Generally speaking, curriculum takes many different forms in schools—too many to comprehensively catalog here.