According to a Goldwater Institute study...

In light of available Arizona data,
statewide school district consolidation
appears ill-advised. A growing body of
national research on consolidation
supports this assessment. Syracuse
University’s Maxwell School Center for
Policy Research scholars Matthew
Andrews, William Duncombe, and John
Yinger recently surveyed three decades
of empirical research on school district
consolidation. They concluded that cost
savings might be achieved by moving
from a very small district (500 or fewer
students to districts of 6,000 or
more students as models of dministrative
savings. Researchers Andrews,
Duncombe, and Yinger caution that
diseconomies of scale begin to emerge
when districts grow larger than 6,000
students, and “sizeable diseconomies of
size may begin to emerge for districts
above 15,000 students.”

 The Syracuse study is not alone.

 In his study of New York
state school districts, economist Herbert
Kiesling concludes that “no evidence has
been found to support the popular idea
of economies of scale in school district
performance.”53 [all footnotes are available at Goldwater web site:
http://goldwaterinstitute.org/Common/Files/Multimedia/401.pdf
James W. Guthrie, now chair of the
Peabody Center for Education Policy at
Vanderbilt University, concluded that
the consolidation trend has generally
failed to produce promised economies of
scale.54 Likewise, William F. Fox,
director of the Center for Business and
Economic Research at the University of
Tennessee at Knoxville, finds much of
the research on economies of scale in
education to be flawed methodologically
and concludes that “size economies
results must be applied cautiously, and
with full recognition of the unique
characteristics of each place, because
considerations [besides size] are vital to
determining the cost implications of
policy decisions.”55
Over 30 years of research indicates
that school district size does not
determine efficiency.

Big District...Big Savings?
 "Writing for the American School Boards Journal, Carolyn Mullins reviewed the pros and cons of consolidation and found consolidation is no “panacea for all education’s ills.”

Mullins concluded,
“Like the bikini, it isn’t
for everybody and never
will be.” (at p. 15 of Goldwater report, supra)