The merger unfolding between two western Pennsylvania public school systems with sharply declining enrollments is the state's first district consolidation in at least 20 years, and most notably, its first voluntary one.

Officials say the move will save money and improve educational offerings, yet parents in both districts worry that some losses will accompany any gains. In any case, the consolidation is expected to be closely watched.

The willingness of two school districts to dissolve boundary lines is rare in states where local school board control is sacrosanct and school traditions that define a community are deeply ingrained. In recent years, at least a few states have tried to force mergers, with mixed results.

Yet the marriage of the Center Area and Monaca school districts northwest of Pittsburgh is part of a gradual, ongoing national progression toward fewer districts educating public school students.

Over roughly the last two decades, the number of school districts nationwide has declined 10 percent, from 15,714 in 1985-86 to 14,166 in 2005-06, according to the National Center for Education Statistics.

With local school boards facing spiraling prices for fuel, employee health insurance and other operating costs — and opposition to increases in property taxes that largely pay for them — the idea of consolidating to save money is becoming an increasingly common discussion topic.