Origins of the school began when the Long Branch Continuation School was established in 1926 as an extension of Long Branch Public School. The front section of the elementary school was added to the building to accommodate a continuation school. This new front section consisted of six classrooms, a board and staff room, a nurse's office and a principals office. The additions were completed in 1930-31 by George Roper Gouinlock, son of prominent architect George Wallace Gouinlock. These new facilities were used by the continuation school. The principal of the Continuation School was Mr. James. S. Bell who served the school from 1926 to 1946. In September 1946, O. Barkley principal of the Continuation School. 1948-1951 were years of expansion for Long Branch Public and Continuation School. The Senior Boys Academic Vocational class began in the fall of 1950. Following World War II, the New Toronto Board of Education proceeded with discussions to build such a school within The Lakeshore Area. The Long Branch Continuation School, which was providing high school education for New Toronto and Long Branch, was struggling to keep up with capacity pressures. Mimico High School, which was business-oriented, was the only other high school operating in The Lakeshore area at the time. For some time it was debated just what form this school should take and finally it was decided to build a combination High and Technical School on Eighteenth Street to be known as New Toronto Vocational School. The building was erected in 1950 and is being opened for classes on September 4, 1951 with the school officially opened on December 7, 1951 by the New Toronto Board of Education. The new building was designed by architect John B. Parkin. The Public School which had been housing classes in the basement rooms, gymnasium and three churches, filled the vacated space. Mr. Rod Jack became vice-principal. A secretary was added to the school staff. In 1953, Long Branch became James S. Bell Public School. Due to the "Baby Boom" of the post-WWII era, additional capacity was required in the Lakeshore high school system. As a result, by 1965, the size of New Toronto Secondary School was almost doubled with additions being erected to meet the needs. Following the extension of public funding to Ontario separate schools in the early 1980s, by the Ontario Government of Bill Davis, transfer of funding and students to Roman Catholic separate schools caused a crisis in public school system. The loss of students required the closure of some public schools. New Toronto Secondary School was originally slated to be closed, however, community action and the facts that the school was centrally located in The Lakeshore and it was the only school with technical shops to teach skilled trades ultimately determined that it would remain as the area's public high school. In June 1983, Alderwood Collegiate Institute in Alderwood closed its doors. New Toronto and Alderwood were merged to form Lakeshore Collegiate Institute. In 1988, Mimico High School closed and all public secondary school students in the Lakeshore area would attend LCI from that time.
