Operational expense goes up as enrollment goes down in D150

I’ve been looking at the Interactive Illinois Report Card for District 150. Here are the total expenditures of District 150 for a period of eleven years, 1997-2008; in the last column, I converted all the amounts into constant 2008 dollars to make it easier to compare apples to apples:

Fiscal Year Actual $ 2008 $
1997-1998 $107,936,064.00 $141,958,238.53
1998-1999 $115,530,704.00 $147,952,054.74
1999-2000 $126,520,944.00 $156,698,726.18
2000-2001 $133,724,155.00 $163,011,857.72
2001-2002 $141,804,220.00 $168,810,141.23
2002-2003 $144,820,439.00 $169,186,245.74
2003-2004 $150,635,231.00 $170,357,567.44
2004-2005 $156,088,426.00 $170,720,248.71
2005-2006 $171,085,329.00 $182,558,995.50
2006-2007 $161,209,034.00 $167,334,977.29
2007-2008 $166,503,198.00 $166,503,198.00

Looking at the inflation-adjusted dollars, and acknowledging that it does appear to have started a downward trend, you’ll nevertheless notice that from 1997 to 2008, operational expense per student has increased over 17%. However, if you look at enrollment over roughly the same period (1998-2009), the trend is different:

Fiscal Year Enrollment
1998-1999 15,258
1999-2000 15,134
2000-2001 14,910
2001-2002 14,910
2002-2003 14,889
2003-2004 15,001
2004-2005 14,701
2005-2006 14,469
2006-2007 13,961
2007-2008 13,642
2008-2009 13,825

I wanted to include the 2008-2009 data so you could see that enrollment did go up slightly that year. Nevertheless, enrollment from 1998 through 2009 fell by 9.4%. As a result, operating expense per student has increased over 24% — from $9,184 in 1997 (in inflation-adjusted dollars) to $11,398 in 2008.

Questions: Why have operational expenses continued to climb while enrollment has been decreasing? Why are expenses $25.4 million more in 2008 than in 1997 (in inflation-adjusted dollars) when enrollment fell by over 1,400 students? Where is the money going?