School organizational models are methods of structuring the curriculum, functions, and facilities for schools, colleges, and universities. The organizing of teaching and learning has been structured since the first educational institutions were established. With greater specialization and expertise in a particular field of knowledge, and a gathering of like-minded individuals, instructors clustered into specialized groups, schools, and eventually departments within larger institutions. This structure spread rapidly during the 19th and 20th centuries with factory model schools and their "assembly-line" method of standardized curriculum and instructional methods. Beginning with the progressive educational movement in the early-mid 20th century, and again with similar trends in the late 20th and early 21st century, alternative models structured towards deeper learning, higher retention, and 21st century skills developed. The organizational models of schools fall into several main categories, including: departmental, integrative, project-based, academy, small learning communities, and school-within-a-school. Departmental model The departmental model is an organization where the departments and faculties of different academic subjects are separate and distinct. Each department (e.g. Math, Humanities, Science) may also have its own head (or manager or dean) that is responsible for different aspects of the department. Educators in that department may report to that head who in turn reports to a higher level administration, such as a school or college in a university, or directly to the main administration, such as the principal or head of a school. Educational institutions using the departmental model often provide traditional education. This is a traditional form of organization with an emphasis on traditional classroom forms and organizations that has been the dominant organizing model of high or secondary schools, colleges, and universities since the late 19th and early 20th century. This is reflected in the design of educational facilities with separate faculty buildings on a campus, or in a wing or cluster of standard classrooms or laboratories in a high school (e.g. science labs, vocational shops). Master's School Building - traditional plan school Integrative model The integrative model is an interdisciplinary organization that combines, rather than separates, academic subjects, faculties, and disciplines. A departmental structure may be in place for each field or discipline, but the physical organization of the educational facilities may place different subject-based classrooms or labs in groupings, such as in a defined area, wing, or small learning community. For example, each grouping may contain co-located classrooms with different instructors focusing on math, English, and Social Sciences