High school students were transferred to other buildings, and in 1931, an addition containing several classrooms, an auditorium, and a gymnasium was constructed.

[6][7] The core block of the Greenfield Union School, constructed in 1914-1916, is a tall, rectangular, side-gabled, Georgian Revival red brick structure on a high basement.

The front of the building has a full-height tetrastyle entry portico, styled in the Corinthian order and topped with a triangular pediment.

[2] Two Georgian Revival wings, built in 1931, flank the main block of the school, giving it an overall H-shaped plan.

[2] The interior of the school features an entry vestibule beyond the main doors, leading to a corridor housing administrative offices.

The gymnasium has tall Palladian windows with wood trim and exposed masonry walls.