Century Schoolbook was originally based on the earlier Century Roman, designed in 1894 by ATF designer Lynn Boyd Benton.Century Roman was commissioned from Benton by the American printer and publisher of Century Magazine, Theodore Low De Vinne, who wanted a clear, legible face for his magazine.
Back in 1892, twenty-three different type foundries had been consolidated to form American Type Founders, and Lynn Boyd's son Morris Fuller was given the task soon afterwards of consolidating and updating the numerous styles and faces that ATF had inherited. In this process, he also took on the task of updating his father's designs, which resulted in his version of Century Expanded, issued in 1900, which proved to be a big success. Century Bold and Italic were issued soon afterward, followed by a Bold Condensed and an Extra Condensed.
When Ginn & Co. approached Morris Fuller Benton and asked for a legible face for its textbooks, Benton utilized research done by Clark University on the letterforms that were most easily identified by young readers. In designing Century Schoolbook, M. F. Benton increased the x-height, the stroke width, and overall letterspacing.An immensely popular face for A.T.F., Century Schoolbook was adapted for Monotype and Linotype systems and later, for digital formats.
If you're interested in early twentieth century textbook publishing, take a look at the short film here about Ginn & Co. It's great!