Just over a decade ago, more male principals could be found at the helm of public elementary schools. But today, according to the most recent stats from the National Center for Education Statistics (NCES), there are more female principals leading public elementary schools. Between 1993-1994 and 2003-2004, the percentage of female public school principals increased from 41 percent to 56 percent in elementary schools. There was also an increase in female secondary school principals—from 14 percent to 26 percent—although the majority of high school principals are still male. The majority of female principals in private elementary schools stayed the same at 68 percent (with about 34 percent leading private secondary schools).
During this same period, the number of K-12 principals in the U.S. increased from 104,600 to 115,000. You can read more NCES stats on principals at http://nces.ed.gov/programs/coe/2007/section4/indicator34.asp.