Founded in 1891 as Plano Public School, serving both primary and secondary students, the school was, by the mid-1910s, sending a majority of its graduating students on to college. Plano High School, created in 1952 by separating the primary students into Mendenhall Elementary School, was immediately accredited by the Southern Association of Colleges and Schools, allowing its graduates to enter college without taking an entrance exam. In 1964, Plano High School integrated with the Frederick Douglass School (formerly Plano Colored School), and the integrated football team won the first of the school's seven state championships in 1965. In 1975, the school moved to a new campus with five buildings, very similar to the layout of a junior college, where it has remained since. The old building is now the T. H. Williams High School, serving 9th and 10th grade. During the first year only at the new campus, PSHS served 10th - 12th grade, making the Class of 1978 the only class to attend school at this campus for three years.