- A high school opened on the second floor of the Easttown School in Berwyn. In June 1896, five students graduated.
- The joint Tredyffrin-Easttown High School opened.
March 5, 1954
- The high school became a junior-senior high school, serving Willistown, East Whiteland, the Borough of Malvern as well as Tredyffrin and Easttown townships.
- Groundbreaking ceremony for new senior high school of The Paoli Area High School System
May 17, 1954
- School board votes to name the new high school Conestoga Senior High School. A contest was held to name the school. A ninth grade student suggested the name Conestoga because the old Conestoga road passed through all six communities which send students to the new school.
October 27, 1954
- Cornerstone ceremony.
June 9, 1955
- Last commencement of the Tredyffrin-Easttown Senior High School
September 9, 1955
- Conestoga High School opens with a student enrollment of 549 and a faculty of 35.
- 19 room addition changed the shape of the high school from "J-shaped" to a "U-shaped" building. Student enrollment was 1036.
- 20 room addition changed the shape to an enclosed rectangle.
- The library was enlarged and named the Karl Zettelmoyer Library in recognition of his years as principal from 1957-1971.
- A new gymnasium, named for John C. Rittenmeyer, principal from 1971-1988, was added as well as a new science wing, and communication center.
- Fourteen general-purpose classrooms and ten science labs/classrooms were added. The cafeteria has been enlarged and modernized. The entire music area was reconfigured. A new 3,660 square foot choral classroom houses the growing choir. There is a new keyboard lab with updated electronic music equipment and new practice rooms. In the family and consumer sciences lab, kitchens were completely reconfigured and renovated. A new and welcoming main entrance includes a spacioius lobby (see picture left) and reception area.
- Outside Conestoga High School, all parking areas were reconfigured and landscaped.
1915-1940: S. Paul Teamer
1940-1952: Wallace S. Brey
1952-1959: B. Anton Hess
1959-1972: Karl A. Zettelmoyer
1972-1988: John H. Rittenmeyer
1988-1989: Clifford Franks, Acting Principal
1989-1994: Daniel Waters
1994-1999: Kaye Pollock
1999-2002: Susan Yates
2002-2009: Timothy Donovan
2009-Present: Dr. Amy Meisinger