Easton's Bible Dictionary

Schoolmaster - the law so designated by Paul (Gal. 3:24, 25). As so used, the word does not mean teacher, but pedagogue (shortened into the modern page), i.e., one who was intrusted with the supervision of a family, taking them to and from the school, being responsible for their safety and manners. Hence the pedagogue was stern and severe in his discipline. Thus the law was a pedagogue to the Jews, with a view to Christ, i.e., to prepare for faith in Christ by producing convictions of guilt and helplessness. The office of the pedagogue ceased when "faith came", i.e., the object of that faith, the seed, which is Christ.