The National Center for Education Statistics 1990-91 Schools and Staffing Survey examined the prior work experience of elementary and secondary public school principals. The survey found that 98.7 percent of principals had taught an average of 10.6 years before taking their administrative positions. The number of years of teaching increased with age; those under 40 spent an average of 8 years teaching, and those 50 or over spent an average of 11.3 years teaching. Nearly half of the principals surveyed, 49.8 percent, held other administrative positions in education for an average of 5.7 years before becoming principals. About 17 percent of the principals held nonteaching, nonadministrative positions such as guidance counselor, librarian, or curriculum specialist before becoming principals, averaging about 6 years in those positions. (JPT)