The school was founded by charter of Philip and Mary in 1555. The oldest sections of the school were built in 1567, formerly referred to as the "big school" and is now used as the school library. South End Site became the model for Boston Latin School which was the first school in what was to become the United States of America. The school still retains the Latin motto 'Floreat Bostona' (May Boston Flourish). This motto also forms the title of the official school song, written by Dr G.E. Pattenden, headmaster from 1850–1887, which he referred to as 'my school hymn'. The song is still sung at official school occasions such as Prizegiving, Charter Day and Beastmart.