It is claimed that District School No. 1, now called The Little Red Schoolhouse, is the only one-room schoolhouse operating in New York State. Built in 1861, it’s just south of Troy near Hudson Valley Community College; this school is the North Greenbush school district. Its survival in the age of school consolidations is remarkable, though it should be noted that it is now only two grades, kindergarten and first. I suspect there was a broader spectrum when this photograph (from the Library of Congress) was taken; it’s undated, alas. I also suspect that most of the studies involved finding the perfect distance from that stove in the winter months. Too close and you were no doubt singed, too far and your toes were frozen.
More on its history here.