The Story Behind the Statistics

By Caroline Hendrie

Behind this year's forecast of record-breaking school enrollment are some statistical quirks that have even veteran education-watchers scratching their heads.

Chief among them is the fact that the total number of children ages 5 to 17, the range that demographers traditionally consider school-age, is actually expected to be smaller this year than when enrollment hit its previous peak 25 years ago.

This year, that traditional school-age group is expected to be slightly less than 50 million, compared with 52.6 million in 1971, said Gregory Spencer, the chief of the population-projections branch of the U.S....