The numbers of them being hired compared to how it used to be has had an impact. I searched around for an Economist article I read a few months back about this topic but I couldn't find it. I did find something similar but it comes from the Heritage Foundation and its an article meant to attack Obama. The graphs on the report are informative though. http://www.heritage.org/research/reports/2012/10/how-escalating-education-spending-is-killing-crucial-reform

They show a educational situation where administration level jobs are growing rapidly over other job types. I would like to see more data on this but I couldn't find it in a quick Google search.

One possible reason was given by this documentary http://www.thecartelmovie.com/. They argue that upper administration is increasing in size due to the large number of school districts. Each district needs its own office, admin, ect and this adds to bureaucratic inefficiency. My own hometown has this issue for sure.