Strictly speaking, projecting means extrapolating on the basis of past trends. Enrolments are projected on the assumption that the trend – whether growth or decline – will continue to evolve as it did in the past. A simple and rapid method to creating a projection is to estimate, on the basis of past statistics, an arithmetical or geometrical rate of increase (or decrease), which is then extended into the future by applying it to the most recent data values. Projections do not attempt to describe what will happen in the future. They only try to present what would happen if such and such conditions were to prevail.
Schools traditionally operated within fixed geographic boundaries; planners used local demographic data in combination with enrollment projection techniques to estimate the number of students a school was likely to serve. However, one of today’s educationalreform trends is school choice—as opposed to school assignment—rendering ineffective the traditional demographic method of projecting school enrollment numbers (Stevenson, 2006: 1).