Devon Preparatory School is a Catholic all-male college preparatory school in Tredyffrin Township, Pennsylvania, in the United States, with a Devon postal address. Founded in 1956 by Piarists, it is divided into a middle school (grades 6–8) and an upper school (grades 9–12), both located on the same 20 acres (8.1 ha) campus. The school operates independently under the auspices of the Roman Catholic Archdiocese of Philadelphia.

The Devon Preparatory School site was originally owned by Philadelphia publisher, art collector, and socialite Charles Matthew Lea, who built his mansion in 1913 that was later to become Calasanctius Hall. Lea, son of historian Henry Charles Lea, inherited his fortune from the Lea & Febiger publishing firm, the oldest publishing company in the United States (1785–1990). The firm's best-known title was the American edition of Gray's Anatomy, which they began publishing in 1859. In 1920, the school expanded the original 20 acres (8.1 ha) tract on the east side of Valley Forge Road by purchasing an additional 83 acres (34 ha). This consolidated property was known as Westthorpe Farm.

The main entrance to Westthorpe Farm was at the intersection of Conestoga Road, Valley Forge Road, and Hunters Lane, where large stone pillars still stand. Several stone pillars that initially formed a southern fence line remain partially in place along West Conestoga and Upper Gulph Roads. The current entrance to Devon Preparatory School, on Valley Forge Road, was the service entrance to the mansion. An outbuilding from Westthorpe Farm still stands northeast of the intersection of Upper Gulph and Hunters Lane.

The 25-room Westthorpe mansion, designed by Brockie & Hastings, was the home of Charles M. Lea until he died in 1927. His widow, Charlotte Augusta Lea, remained at the mansion until she died in 1945.

The property was then sold to Alexander Shand, a developer who built one of the first post-World War II developments of homes known as the Shand Tract on Steeplechase Road and Hunters Lane. Shand sold the mansion to Joseph Lerner, who had hoped to make it a psychiatric hospital. Because of neighborhood opposition to his project, Lerner sold the property to the Priarist Fathers in 1955.

In 1994, Father James J. Shea became the school's headmaster. He retired on July 31, 2015. In August 2023, the school announced that Father Francisco Aisa would be stepping down as headmaster to return to his home country of Spain. Father Nelson Henao will become the new headmaster.

Graphs are unavailable due to technical issues. Updates on reimplementing the Graph extension, which will be known as the Chart extension, can be found on Phabricator and on MediaWiki.org.

Enrollment by Race/Ethnicity 2019–2020

White	Asian	Black	Hispanic
246	26	10	8

Previously the school had a boarding program. This ended in 1970.

The campus is in Tredyffrin Township, Pennsylvania. It is adjacent to, but not inside, the Devon census-designated place. Prior to 2010, Devon was in the Devon-Berwyn CDP.

It had a combined barn and residence, in a U-shape, using the French Normandy architecture style. The facility was constructed in 1910. At some point the school sold the land. The barn was later restored into a full residence.

Devon Prep's athletic teams compete in the Philadelphia Catholic League (12 teams).

• Fall: Cross Country, Soccer (Varsity, Junior Varsity, and Freshmen), Golf (Varsity and Junior Varsity), and Crew.
• Winter: Basketball (Varsity, Junior Varsity, and Freshmen), Indoor Track, Bowling, Squash, Ice Hockey, and Swimming.
• Spring: Baseball (Varsity and Junior Varsity), Lacrosse, Track and Field, Tennis, and Crew.

Devon Prep has won multiple championships, which include the following:

• Golf:
  • 2022 PIAA 2A INDIVIDUAL GOLF
  • 2021 PIAA 2A GOLF
• Basketball:
  • 2022 PIAA 3A BASKETBALL PIAA
• Baseball:
  • 2014 PIAA 1A BASEBALL
  • 2019 PIAA 2A BASEBALL
• Tennis:
  • 2021 2A PIAA DOUBLES

Devon Prep has over 50 different extracurricular activity groups. Some of them include: Mock Trial, Model United Nations, Science Olympiad, Film Club, Devon Dialogue (newspaper), Calasanctian (yearbook), Art Club, and many more. There is an elected Student Council, honor societies, and an Academic Challenge Team. Musical groups for students include Jazz Band, Rock Band, Choral Tide, and Rip Tide. There is an annual Fall Drama and Spring Musical.

In the summer, Devon Prep hosts a Summer Enrichment Program. Students participate in sports and dramatic arts camps and various other courses throughout the two sessions. They attend classes including algebra readiness, digital photography, painting and sculpting, video production, study skills, web building, and history explorations. The sports camps include baseball, soccer, track, golf, and basketball.

• Raymond Geuss, philosopher, professor at Cambridge University
• Mark Malseed, co-author, The Google Story and a named collaborator, with author Bob Woodward, on the #1 New York Times non-fiction bestsellers Plan of Attack and Bush at War.

• Piarists
• St. Joseph Calasanz – founder of the Pious Schools and the Order of the Piarists
• List of high schools in Pennsylvania

• Official website