Looks like this was a city school, possibly 2- or 4-rooms. Built 1915, now used as library and museum.
Susan Gosse Leibold provided this information on FaceBook:
This was the public school built in 1915. Nine grades were taught at that time with 10th grade added in 1918, 11th grade in 1919 and 12th grade in 1927. The gym next door was added in 1950. Fort Atkinson Public School existed until 1960. At that time, Fort Atkinson joined the new Turkey Valley School District. Even though the local history book doesn't say it, I know kindergarten students went there for awhile -- Turkey Valley didn't have kindergarten - because my husband went to K there in 1974. Today it houses the public library and Fort Atkinson Museum, and meeting rooms downstairs.
This last photo is of the back side.