Enrollment in the North Hills School District is expected to decline by 7.5 percent over the next eight years, according to a study conducted by a Carnegie Mellon University professor.

By 2016, enrollment is projected to be 4,409, down from 4,768 this school year, said Shelby Stewman, a professor of demography and sociology at CMU.

Superintendent Joe Goodnack said the findings were not surprising, considering that families are getting smaller, the community is aging and the region's population is declining.

"It's a gradual decline," he said. "It just basically confirmed what we thought."

Dr. Stewman presented his findings to the school board April 16. The district does not yet have an exact cost for the study, but it is expected to be $3,000 to $6,000.

The research presented by Dr. Stewman was a follow to a 2003 study commissioned by the school district, which serves Ross and West View, to determine future building needs. The earlier study also predicted a population drop, but not as dramatic as the most recent figures.

Dr. Goodnack said the most recent study, which found elementary enrollment to be declining more dramatically than originally anticipated, reinforces the district's decision to close three elementary schools and focus resources on improving the remaining four elementary schools.

The district also is renovating North Hills High School, a $26 million project that is expected to be completed before the start of the 2007-08 school year.

Early in 2008, renovation projects for the elementary schools are planned, including closing Perrysville, Northway and Seville elementary schools.

The remaining elementary schools -- Highcliff, McIntyre, West View and Ross -- will be renovated.

Dr. Goodnack said the decision on closing elementary schools considered not only the demographic study but also the deteriorating conditions of the buildings and projected tax revenues.