The Archdiocese of Philadelphia's announcement yesterday that it would close dozens of Catholic schools this year was the big news story yesterday. Many factors were cited, ranging from competition from charter schools to rising costs to declining enrollments, which have plunged 35 percent in the last decade in the Archdiocese.

But one overlooked factor contributing to the rising costs of Catholic schooling is the decline in nuns, one way that Catholic schools traditionally kept their personnel costs low. New Jersey freelance writer Jen A. Miller captured this dynamic in this 2009 story in New Jersey Monthly.

"The decline in teaching clergy is due in large part to the steep drop in the number of nuns. As nuns—and priests—die and are not replaced by new clergy (91 percent of nuns are 60 or older), schools must hire replacement staff. Catholic schools are not required to use state-certified teachers, but they do need to pay faculty salary and benefits—something not required for clergy.

The result: The average Catholic school tuition has more than doubled since 1990. It has now reached $3,159 per elementary school student and $8,182 per high school student, according to the United States Conference of Catholic Bishops."