In 1904, Mr. Allen met Robert Alston Stevenson, a tutor, who by chance had taken a room at 509 Fifth Avenue, where the School was then located.

In 1924, the School purchased two brownstones for a new schoolhouse and moved to its present location on the Upper East Side.

The School introduced team sports at Randall's Island and required boys to wear navy blue blazers and gray flannel pants.

Allen-Stevenson's school song was composed by Rolande Maxwell Young in 1968, the year she joined the A-S faculty as a lower-school music teacher.

Around that time an East 77th Street addition, designed by A-S parent Alfredo De Vido, was built onto the school.

This made Allen-Stevenson the very first elementary school in the United States to achieve LEED-EB Gold status.

A key part of their theater program, is the annual Gilbert and Sullivan musical performed by members of the sixth through ninth grades.