A Fascinating Claim

From the July 10, 2012 Wall Street Journal:

Since 1970, the public school workforce has roughly doubled—to 6.4 million from 3.3 million—and two-thirds of those new hires are teachers or teachers' aides. Over the same period, enrollment rose by a tepid 8.5%. Employment has thus grown 11 times faster than enrollment. If we returned to the student-to-staff ratio of 1970, American taxpayers would save about $210 billion annually in personnel costs.

The author, Andrew Coulson, points out that this dramatic expansion isn't because of the mainstreaming of special education kids:

Nor can the explosive growth in public-school hiring be attributed to federal spending on special education. According to the latest Census Bureau data, special ed teachers make up barely 5% of the K-12 work force. 

Where did this dramatic expansion of teachers relative to students go?  When I was in elementary school, there were usually 30 or more students per class.  Today, most classrooms are still extremely crowded.  Either nearly all of this astonishing growth is just teachers' aides, or there are a lot of public school teachers with nearly empty classrooms to make up for the ones that are still teaching 30 students.

Is Coulson right about this?  Have we really dramatically expanded the number of public school employees relative to the students (with little or no net improvement in results)?  If so, where are those teachers?

Here's the National Center for Education Statistics table showing historical population characteristics.  In 1969-70, there were 45,550,000 elementary and secondary school students in the U.S.  In 2005-06, there were 49,113,000.  That's a 7.8% increase in students, so the 8.5% increase that Coulson claims might bring us to this year.  The same table shows total instruction staff for 1969-70 at 2,406,000, and 4,151,000 in 2005-2006.  That's a 72.5% increase in instructional staff.  Coulson's unbelievable numbers seem to be correct.