Until within the last few years, public schoolhouses in American cities and towns were open only for the regular school work and for children of legal school age. However, since the beginning of the present century, there has been a growing interest in public school extension and for a fuller use of the public school plant. In most cities and large towns, schoolhouses are now used for night schools, both for older boys and girls and for adults, for meetings of civic societies, for entertainments, for meetings of parent-teacher associations, and other similar educative purposes. It is not uncommon for public school funds to be used directly or indirectly for the promotion of these larger and less organized forms of education. To meet the demand for some intelligent account of the nature and progress of this movement for the extension of public education and the wider use of school buildings, this bulletin discusses what it is that is being extended and the extent of the extension movement. A copy of the circular letter inviting the superintendents of schools to participate in the study is provided in the appendix. (Contains 9 tables, 11 plates, 2 figures, and 5 footnotes.) [Best copy available has been provided.]