Trinity College School was founded in Weston, Ontario. It officially opened in the home of William A. Johnson, the School's founder, on May 1, 1865. There were nine students and faculty. The school grew, and in three years' time larger quarters were needed.
The leading citizens of Port Hope, anxious to have the School located in their town, offered to pay three years' rent on premises suitable for a school. The offer was accepted and Trinity College School opened in Port Hope in September 1868.
During the next thirty years, under the direction of Headmaster Charles Bethune, Trinity College School grew from the motley collection of wooden sheds and buildings which existed initially at the site in Port Hope into a prosperous, thriving academic community.
On a wintry night in 1895 an explosion of a coal oil lamp in one of the master's rooms started a fire which destroyed almost the entire School. No one was hurt and the School was rebuilt in only eight months.
A second disastrous fire occurred in 1928. Again, virtually all of the School was destroyed. But rebuilding the School was not an easy task this time. Although TCS had received promises of funds to help with the reconstruction from the Old Boy community, on the heels of the fire came the Great Depression and many Old Boys had to withdraw their promises.
In 1933, Trinity College School's newly appointed headmaster, Philip Ketchum, found himself in charge of an institution on the brink of bankruptcy. He spent the first few years of his tenure trying to raise funds to pay off a very onerous mortgage. But, through the generosity of a handful of Old Boys, the debt was finally retired.
Throughout the mid-century period, the School experienced tremendous growth in both admissions and facilities under the leadership of Headmaster Ketchum and Junior School principal Charles Tottenham.
Due to the declining enrollment of younger students, the Junior School was closed in 1981 and Charles Tottenham retired. In 1991 The School became co-educational, enrolling its first female students. The Junior School would re-open in 1999 under the leadership of Junior School Head Barbara Piccini.
Today, Trinity College School prepares both boarding and day students for post-secondary education at universities around the world.