Last week, the Division of Non-Public Education (DNPE) released the 2015-16 enrollment totals for private and home schools.

Home school growth has been phenomenal for years, but the last two have been nothing short of amazing.  In 2015, home school enrollment eclipsed the 100,000-student mark after adding nearly 8,700 students, compared to the prior year estimate.

This year, North Carolina had an estimated 118,268 home school students, a staggering increase of 11,415 students or nearly 11 percent.

So, why is home schooling growing faster than Taylor Swift’s Girl Squad?  It depends on the values and circumstances of each family.  Some are not satisfied with the academic quality or social environment of their assigned public schools.  Others object to the inculcation of secular values embedded in the public school curriculum.  Still others seek an alternative to the homogenization, regimentation, and depersonalization that typify modern public schooling.

Parents send their children to private schools for many of the same reasons.

Private school enrollment inched up by roughly 500 students to 97,721.  After years of enrollment declines and only negligible increases over the past two years, private school enrollment finally exceeded the pre-recession enrollment peak of 97,656 students.

It is likely that the Opportunity Scholarship and Disability Grant programs, which provide private school vouchers to eligible low-income and special needs students, are responsible for some of the recent growth in the private school population.  The N.C. General Assembly just approved substantial funding increases for both programs, so total private school enrollment may soon surpass the 100,000 student threshold.

While home and private schooling certainly benefit the families that choose those options, the real winner is the North Carolina taxpayer.  Home and private school families pay taxes to support public school systems that they have every right to use but don’t.

I’m often asked to calculate the savings realized by keeping over 200,000 children out of public system.  But it is not as easy as multiplying the total number of students by the district or state’s average per-student expenditure.  Why?

To get the most accurate figure, one would need to account for the location, grade level, educational needs, access to public charter schools, and the capacity of schools assigned to home and private students.  It is possible, for example, that school districts could absorb a number of incoming students without affecting facilities, staffing levels, and other fixed costs.  In those cases, the cost of adding one additional student to the system, which nerdy researchers call the “marginal cost,” would be relatively low.

On the other hand, some school districts would find that number of incoming students would exceed what they, using existing resources, could provide.  In these cases, districts would need to build schools and hire additional teachers and staff, thereby raising the marginal cost of educating those children.  Theoretically, our fastest growing and largest school districts would have the toughest time accommodating an influx of home and private school students.  Their marginal costs, and thus savings to taxpayers, would be much higher.

In separate studies, Alex Grecu, Cotton Lindsay, and Andrew Coulson argue that the marginal cost of educating a student is between 80 and 85 percent of average per-student spending.  In other words, between 15 and 20 percent of the costs of educating a student are fixed.  The remaining costs are variable. Please note that there are disagreements about the marginal cost calculation.  In a 2012 study published by the Friedman Foundation, for example, Ben Scafidi found that the short-term variable cost for North Carolina was 67.6 percent.  Some researchers argue that the percentage of fixed costs are much higher, even constituting the majority of the marginal cost.  For now, I will calculate the marginal cost using both the 67.6 percent and the 80 percent figures.

North Carolina’s 2014-15 per-student expenditure (latest available) was $9,235 for both operating and capital expenditures.  The marginal cost would be between $6,242,86 (67.6 percent) and $7,388 (80 percent) per student.  Using this rough estimate to create another rough estimate and ignoring the many methodological issues involved in such an exercise, home and private schools saved taxpayers an estimated $1.35 t0 $1.58 billion last year.

So, there you have it.  Home and private school students save taxpayers between $1.35 and $1.6 billion last year.  This taxpayer really appreciates it!