1906 – A new wing containing six rooms was added to the stone building.
1923 – In 1922 the Corner Stone of the “new” school was laid. The school was opened in September, 1923 at the cost of $450,000. It was built upon the ground formerly occupied by the cedar swamp and the creek. It featured a swimming pool in the basement 60′ long and 24′ wide, an ‘open’ auditorium in the centre with a glass skylight in the roof and a balcony. The pool was later drained due to leaking. The basement area was converted to a storage area and cadet rifle range.
1926 – The first school yearbook, “Acta Nostra” was published and the meaning of its Latin name is “Our Doings.” The Acta Nostra was not published due to the lack of funds from 1934 to 1941.
1929 – The G.C.V.I. crest was designed by a student and first appeared on the cover of the 1929 Acta Nostra.
1931 – Principal and staff take a voluntary pay cut because of the Great Depression.
1946 – A passage way was built in 1946 connecting the 1923 building with the original 1906 limestone structure.
1959 – The old limestone school (1879, plus the 1906 addition) was torn down to make room for a new wing. The old gym was taken apart.
1960 – A new addition, classrooms, cafeteria, double gym was open.
1959 – 1962 – A new commercial wing was added and main office. The library was expanded.
1969 – The swimming pool was converted to the library, and named the P.G. Reid Resource Centre. The Archives was part of the original plan for the library when it opened. The guidance office moved into the former library.
1970 – The credit system was introduced to the school.
1974 – Renovations happened to the auditorium to remove the skylight and close-in the surrounding walls. At the back of the auditorium the balcony became the seminar rooms. The main office was renovated.
1975 – G.C.V.I. became one of the first schools in Ontario to move to the semestered school year.
1976 – George King was a G.C.V.I. staff member. His initiative led to the forming of what was to be known as Co-operative Education.
1979 – The addition of the tennis courts were added to the back campus. This was a joint venture between the Board of Education and the City of Guelph.
1980 – The grade 13 art class designed a memorial mural honouring the memory of former G.C.V.I. students who gave their lives during World War I and II.
1983 – A labour of love began as the original stonework of the archway from 1879 and its 1906 addition was unearthed by Clare Newson’s students in 1985. The arch was reconstructed in 1991 to create a ceremonial entrance to the auditorium. The project was completed in 1993 with the installation of the oak doors and plaques. This entranceway is a lasting tribute to the long tradition of educational excellence at The Guelph Collegiate-Vocational Institute and to future generations who will pass through these doors.
1984 – A Time Capsule was buried in the Japanese Gardens and would be dug up in 2004 commemorating the sesquicentennial year of the school beginning in 1854 on the Yorkshire St site.
1985 – A secondary school teachers strike in Wellington County lasted 51 days from September 16 to November 25.
1994 The 140th Anniversary Reunion took place.
1996 – The Wall of Fame was unveiled. The Wall, located in the school’s main corridor acknowledges and recognizes the contributions of G.C.V.I. Alumni who achieved local, national or international fame.
1997 – The effects of Bill 160 were feared by everyone in the education system. A teacher protest lasted from October 27 to November 7.
1998 – Secondary school teachers were on a one day legal strike on September 18 in Dufferin and Wellington Counties.