Hornbook. Paper was scarce and expensive during the Middle Ages and until the early 1800's. It had to be used sparingly. The hornbook was invented to protect the paper on which the first lessons of young children were printed. It was used as early as 1442. By the end of the 1500's, the hornbook was standard equipment in English schools. Use of the hornbook continued in England and America until about 1800, when books became cheaper. Today, hornbooks are rare collector's items.