Doesn't seem high to me. I recall that my school district replaced the HVAC system while I was in high school and the ROI paid for the new multimillion dollar system in something like 5 years.
That 800,000 sq ft is for an entire district. With a little searching, I found that Saline High School is the single largest school in Michigan at 480,000 sq ft. Most large schools seem to be in the low hundreds of thousands.
So the $100k/mo figure is probably high by a few factors - maybe an order of magnitude at most.
http://www.schoolenergysaving.com/schoolEnergyFacts.php
"A mid-sized school district with 800,000 square feet of space pays more than $1M annually for energy."
"Space heating, cooling, and lighting together account for nearly 70% of school total energy use."