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Proiected Student Enrollment 2006-2011 <br />Enrollment projections are generally most accurate for the initial years of the forecast period. <br />Beyond the 5-6 year range, projected assumptions about economic or demographic trends may <br />prove false, resulting in an enrollment trend that is quite different from the projection. For this <br />reason is important to monitor birth rates, new housing construction, and population growth on <br />an annual basis as part of facilities management. In the event that enrollment growth slows, <br />plans for new facilities can be delayed. It is much more difficult, however, to initiate new <br />projects or speed up projects when enrollment growth exceeds projections. For this reason, it is <br />sometimes useful to project slightly more growth than might be expected so as to be better <br />prepared for future events. <br />The Growth Management Act (GMA) requires that planning for public facilities be consistent <br />with the 20 -year population projections developed by the Office of Finance and Management <br />(OFM) for the State of Washington. This element of the GMA has been interpreted to mean that <br />the OFM population forecasts are minimums that must be accommodated. <br />The District has contracted with a consultant to develop a methodology for projections. The <br />consultant has an sixteen -year history of working with local school districts in doing projections, <br />including seven years as the demographer for the Seattle Public Schools and nine years as an <br />independent consultant providing long-range projections for the Highline, Edmonds, Puyallup, <br />Federal Way, Marysville, Seattle, Northshore, Bethel and Mukilteo school districts. The <br />methodology employed by the consultant is a variation of the cohort survival method. Cohort <br />survival compares enrollment at a particular grade in a specific year, to the enrollment at the <br />previous grade from the prior year. For example, enrollment at the first grade is compared to the <br />previous year's kindergarten enrollment. The ratio of these two numbers (first grade enrollment <br />divided by kindergarten enrollment) creates a "progression ratio" providing a summary measure <br />of the in -and -out migration that has occurred over the course of a year. This ratio can be <br />calculated for each grade level. Once these ratios have been established over a period of years <br />they can be averaged and/or weighted to predict the enrollment at each grade. <br />Cohort survival works well for every grade but kindergarten where there is no previous grade to <br />use for comparison. At the kindergarten level enrollment is compared to the birth cohort from <br />five years prior to estimate a birth -to -k ratio. This ratio, averaged over several years, provides a <br />method for predicting what proportion of the birth cohort will enroll at the kindergarten level. <br />The District's percentage of this cohort has varied considerably over the past 7 years from a high <br />of 14.2% to a low of 11.8%. Future forecasts assume that the percent will range from 11% to <br />12%. <br />Cohort survival is a purely mathematical method, which assumes that future enrollment patterns <br />will be similar to past enrollment patterns. It makes no assumptions about what is causing <br />enrollment gains or losses and can be easily applied to any enrollment history. For this reason, <br />cohort survival is a useful tool that anyone can use for projecting school enrollments. <br />Despite these advantages, cohort survival can produce forecast errors because it does not <br />consider possible changes in demographic trends. New housing, in particular, can produce <br />enrollment gains that might not otherwise be predicted from past trends. Or, alternatively, a <br />district may lose market share to private or other public schools. It is also possible that a <br />slowdown in population growth will dampen enrollment gains. This appears to be what <br />12 <br />