After years of decline, the number of students expected to attend Island public schools is predicted to grow once again.

A new report forecasts that enrollment in the Mercer Island public schools is expected to remain flat through 2012, then increase by some 600 students through 2020. The rate of enrollment growth is expected to accelerate beginning in 2015 and continue beyond 2020. The forecast suggests that another 300 students could enroll at Island schools after 2020, representing a total increase in enrollment of more than 20 percent by 2025.

Enrollment for the Mercer Island School District was 4,047 last October.

Those future enrollment levels, however, still remain below the record levels of enrollment in the mid-1970s, when the children of baby boomers crowded schools throughout the country, including Mercer Island. Island schools then had more than 1,300 students — or one-third more students — than it does today.

A consultant, Les Kendrick of the Education Data Solutions firm, was hired for the study. Kendrick was the demographer for Seattle Public Schools in the 1990s and has been a consultant to school districts throughout Western Washington since.

The number of students in the district reached a high of some 5,400 in 1974 before steadily declining to 3,400 in 1987. The children of baby boomers filled the classrooms in the late 1960s and 1970s, but had fewer children of their own to take their place. As birth rates have fallen across the board, so has the number of students attending school here. Other school districts across King County, particularly Seattle Public Schools, have seen the same trends.

Enrollment here recovered somewhat since that time, rising to 4,400 in 2000, but has consistently fallen downward.

Over the past several years, incoming kindergarten classes have been consistently smaller than the class that graduates each year, leaving fewer students to fill the grades as they go through the system. Some of the difference has been made up by students who have moved to the Island partway through their education.

In the period between 1990 and 2000, enrollment in King County public schools grew by 30,000 students. Within Mercer Island, enrollment also surged by 1,000 during that time. Since 2000, however, the number of school-age students in King County grew by just 5,600, while Mercer Island enrollment declined by 300 students. Total enrollment within the district has flattened out at around 4,000 students. In response to the decline in students, which means that less revenue comes from the state, district leaders made the decision to bring in students from outside of the district. Some 100 students from as far away as Snoqualmie and South Seattle have enrolled in Island public schools.

The Island population has stagnated for the past decade or so, producing fewer school-age children. There was little or no net new construction of housing on the Island, and existing residents who have remained in those households are older and have adult children.

But the pendulum is swinging back.

New state data reveals that the Island has gained 300 people in each of the past three years.

The number of births in King County over the past five years has averaged at 22,000 each year. Yet in 2006, the number of births jumped to 24,000, providing evidence of a higher rate of births. And since Mercer Island usually represents 1 percent of all county births, approximately 240 students could be entering kindergarten here in 2011-2012. Adding to that evidence, U.S. Census and county data indicate that the number of housing units on Mercer Island has grown to 9,300 from 8,800 in 2000.

Tempering that trend, Kendrick does not expect that the new housing on the Island will affect enrollment significantly since it is primarily multifamily housing and is not marketed to families with children. Why is forecasting enrollment so important? First and foremost, as enrollment declines, fewer state dollars are allocated to the district. The district, left with fewer dollars, must look carefully at costs and see where it can cut back without affecting its ability to educate students. But smaller class sizes are not necessarily the result. Administrators are forced to look carefully at costs and determine how best to keep costs low. By far, the largest single expense of the district is labor.

The school district hired a consultant to conduct a demographic survey to estimate the number of students coming into the district, not only for budgetary purposes, but to figure out if any new facilities need to be built. Superintendent Gary Plano sent a letter to Pixie Hill Preschool and Little Acorn Day School, which both lease space on district land near Youth Theatre Northwest. The letter warned them that the district may want the facilities back which it is presently leasing from them. However, Plano contacted the tenants again last week to withdraw the notice for now.

The district anticipates that it may need more than new classroom space. Despite the fact that there are relatively fewer students than in the past, the district is charged with meeting the needs of all students and must provide special education services here or pay for services outside Island schools if they cannot be provided. Over time, meeting those needs has become more complex and more expensive.

Loss of students to private schools is not expected to have much of an impact on overall enrollment.

Private school enrollment has increased from 286 students in 1993 to 642 students in 2006. Kendrick expects that the number of Island students in private schools will continue to increase slightly; however, as a percentage of total public enrollment, the impact will remain small.

For more information, go to www.misd.k12.wa.us.