District School No. 3 (Castleton on Hudson, New York)

District School No. 3 is a historic one-room school building located at Castleton-on-Hudson in Rensselaer County, New York. It was built in 1870 and is a one story, rectangular massed, brick building in the Italianate style. It remained in use as a school until 1951. Also on the property is a gable roofed garage (1931), a coal / wood shed, and a stone capped well.

It was listed on the National Register of Historic Places in 1998.