In 1563 Sir Roger Manwood founded a Free Grammar School in Sandwich to make education accessible to the townspeople. Since 1563 a great deal has changed. The original school building still stands, but the School has occupied its present site since 1895.

In creating his new Free School in Sandwich, Sir Roger Manwood ensured that it would have firm foundations. The present School is hugely indebted to his foresight - there are four Foundations which still today appoint Governors: the Lord Warden of the Cinque Ports, Lincoln College, Oxford, Gonville and Caius College, Cambridge, and the Diocese of Canterbury. Sir Roger Manwood's inspiration lasted two and a half centuries, into a mid-Victorian era which saw the School, like many Elizabethan foundations, drift into anonymity.

In 1890 the Charity Commission issued an ultimatum: either the Manwood endowments be used to revive the School, or they should be used for general educational purposes. Thomas Dorman, thrice Mayor of Sandwich, was the major benefactor in the revival, and by 1895 the new Manwood Road site was ready for occupation. This is the thirty-acre site of the present school, and from the sixteen boys who entered in 1895 the School has grown to over 1033 boys and girls. The first girls joined the school in 1983.

In September 1992 Manwood's became Grant-Maintained, keeping its Founder's intention firmly in mind: to offer as broad an education as possible, with special emphasis on the pupils' academic development. In 1999 the School assumed Foundation status. In 2003 the school was awarded Language College Specialism and in 2008, as a High Performing Specialist School, the second specialism of Maths and Computing. On 1 March 2011 the school became a Converter Academy. Also in 2011 the school lost its specialist school status due to the initiative being withdrawn by the government, but these subject areas continue to thrive, with four languages being taught (French, German, Spanish and Chinese) and healthy numbers studying both Mathematics and Further Mathematics at A Level.

Though a non-denominational school, Manwood's has had close links through the centuries with St Clement's Church, whose Rector is a member of the Governing Body. This is one of the several strong community connections which make Manwood's precisely what its founder intended.

The late 1990's saw the beginning of a major building programme improving the quality of provision for the pupils across the whole curriculum. This process continues today. The additional facilities created include four well-equipped Science Laboratories, a refurbished Library and Multi-Media Resource Centre, a Technology Block, new classrooms and offices dedicated to the History and R.E. Departments, a hard-play area, an astro-turf pitch and a four-badminton-court-sized Sports Hall. ICT facilities have also significantly developed during this period. In 2005 the Music Department's facilities were doubled in size and in 2008 the five older science laboratories were refurbished, bringing all nine up to a top class standard.