Why are we adding teachers when enrollments are down?

Two often cited statistics are the steadily decreasing public school enrollment and the steadily increasing public school staffing level. Here are some basic facts:

From 2001 to 2006, total public education staffing (i.e. not just teachers, but all jobs needed to operate a school system) has increased by 5.4%. (details here).
From 2000 to 2006, regular classroom teacher staffing has increased by only 1.3%.
From 2000 to 2006, public education enrollment has decreased by 8.1% (details here).

So if the staffing growth isn't coming from classroom teaching positions, where is it coming from? Some of the areas showing the most significant growth include:

aids, ungraded & itinerant teaching positions (13.7% increase)
attendance & social work personnel (97.8% increase)
guidance counselors/directors for grades 7-12 (16.7% increase)
psychologial, speech pathology, and audiology staff (28.2%)
administrative assistants and clerical staff in schools (13% increase)
assistant principals (15% increase)
bookkeepers (23.4% increase)
Special Education Directors (20.3% increase)
statistical and data processing staff (211.3% increase)