Christianity treats teaching as one of the great ministries of the church. As a consequence, Christian education is one of the largest and oldest continuously functioning educational systems in the world, comprising schools and colleges in over 140 countries. It is also the least studied in terms of its impact on curriculum, literacy, teacher training, and professional standards. The Encyclopedia of Christian Education is the first reference work devoted exclusively to chronicling the unique history of Christian education, illustrating how Christian educators pioneered such educational institutions and reforms as universal literacy, home schooling, Sunday schools, women's education, graded schools, compulsory education of the deaf and blind and kindergarten.