Francis Bellows Allen founds The Allen School at a home on Fifth Avenue and 57th Street. Its first class enrolls three boys.
The School moves to rented rooms at Madison Avenue and 44th Street after its enrollment grows to 20 boys.
Six teachers educate The Allen School's 50 students. Mr. Allen meets Robert Alston Stevenson, a tutor, who by chance has taken a room at 509 Fifth Avenue, where the School was then located.
Mr. Allen and Mr. Stevenson join forces and move to 50 East 57th Street with 100 students.
Enrollment exceeds 200. The School publishes its first newspaper, The Spotlight, and introduces an exercise program and team sports.
The School purchases two brownstones for a new schoolhouse and moves to its present location on East 78th Street.
After 56 years of service, Mr. Allen retires at age 80.
Annual Gilbert and Sullivan productions begin.
Mr. Stevenson retires after 43 years of service. His son, Mr. Robert "Huck" A. Stevenson Jr., a teacher at the School since 1924, succeeds him as Headmaster.
Mr. Joseph C. Renard becomes Headmaster of Allen-Stevenson and serves for nine years. The School introduces team sports at Randall's Island and requires boys to wear navy blazers and gray flannel pants.
The Parents Association is founded. Stanley Gauger, the new Music teacher, starts the Allen-Stevenson Orchestra.
The School buys adjoining townhouse and eventually renovates it for school use.
Mr. Henry D. Tiffany Jr., becomes Headmaster and serves until 1974. Under his leadership, a modern Science lab and a paneled library, a gift from the Bell family, are added.
The School begins to use a carriage house on East 77th Street for Art, Shop, and Music. First annual Shakespeare production begins.
The School's enrollment reaches 270 students.
Mr. Desmond Cole becomes Headmaster and serves for 16 years. During his tenure, he appoints Department heads and creates the Middle School division.
The Allen-Stevenson School expands its space into what is known as The Monroe Building.
The School's first computer lab opens.
The Allen-Stevenson School celebrates its first 100 years and publishes The Allen-Stevenson Centennial Album.
Following a Long Range Planning recommendation, the School reintroduces Kindergarten classes, housing them in newly designed classroom spaces in the Monroe townhouse.
The Board of Trustees appoints Mr. David R. Trower as Allen-Stevenson's 7th Headmaster.
The Learning Resource Center is established to bring an awareness of the various ways in which boys learn and to "support and enrich the learning of every Allen-Stevenson boy."
Operation Update, a mini-capital campaign, strengthens the book collection and card-catalog of the Bell Memorial Library and updates telephone and computer systems.
New construction adds three floors and a regulation-size Upper Gym above the 77th Street buildings. Improvements also include a larger computer room, art studio, music room, woodshop, and locker room.
Enrollment is at 376 students, a record-breaking number. The School's Capital campaign, Building for the Future, raises a record total of $5.87 million. A vision statement on the role of technology at Allen-Stevenson is adopted.
The School's Board of Trustees adopts a strategic Long Range Plan that focuses on strengthening The Allen-Stevenson School in the new century. Laptop computers are distributed to teachers to enable them to use technology for teaching and learning.
Allen-Stevenson launches its first website to improve communication about the School.
The Campaign for Allen-Stevenson: Today and Tomorrow, designed to meet the goals of the Long Range Plan, is officially announced.
Allen-Stevenson completes comprehensive renovation of its facilities, adding new space, students and program scope. Enrollment approaches 400 boys. New, more robust version of the School’s website is prepared for launch.
The Campaign for Allen-Stevenson: Today and Tomorrow concludes exceeding goal to raise at least $25 million with final tally at $27.9 million. For the first time in Allen-Stevenson’s history, the enrollment exceeds 400 students. School’s mission statement is rewritten in preparation for NYSAIS Decennial Evaluation in April 2007.
Allen-Stevenson begins year-long celebration of its 125th year. Video timeline of the School’s history is introduced in four segments on a monitor in the Main Hallway. NYSAIS Decennial Evaluation is completed with flying colors.
School completes year-long celebration of 125th Anniversary. The Board of Trustees approves Allen-Stevenson and Its Community, a policy statement about inclusion and community life.
Allen-Stevenson hosts the first meeting of New York City independent schools to form the Green Schools Alliance, which now encompasses thousands of public and private schools across the United States.
A policy on social networking is developed after extensive faculty and administrative discussions. Also, six faculty/staff task forces begin significant, cross-divisional discussion in each of the following areas:
• Families: Working with Families—Education, Communication, Expectations;
• Finance: Financial Sustainability;
• Gentlemen: Becoming a Gentleman and a Good Global Citizen;
• Learning: Excellence in Learning;
• Professional Growth: Professional Excellence and Growth; and
• Teaching: Instructional Practices.
Further, Allen-Stevenson is twice recognized for its work on energy and the environment, first with a coveted Energy Star rating by the U.S. Department of Energy and then by the U.S. Green Building Council (USGBC) for LEED Gold Certification for Existing Buildings (EB). This makes Allen-Stevenson the very first elementary school in the United States to achieve LEED-EB Gold status.
 For explanation of LEED (which stands for “Leadership in Energy & Environmental Design”) please see the website of the USGBC at the following: http://www.usgbc.org/Default.aspx
Two interactive displays are installed in the Main Hall to allow the Allen-Stevenson community to search through athletic team photos going back as far as the 1960s.