The school was founded in 1947 as the
Chesham Technical School - a result of the
Education Act 1944 which set up the tripartite arrangements of grammar,
technical and
secondary modern schools. The all-boys' school was originally housed in only one building, which is now the sixth form block known as "The Curtis Centre". In 1961, the school became known as
Chesham Technical High School. In 1970, the school changed its name to
Chesham High School as it moved away from its technical roots. The name of the school changed to
Chesham Grammar School on 7 May 2010. The rebranded CGS underwent expansion. The school was rated outstanding in all categories by OFSTED in March 2014.
Headteachers • Sidney Chapman (1947–1966) • Paddy Evans (1966–1967) • Ken Stokes (1967–1992) • Tim Andrew (1992–2007) • Nigel Fox (2005–2006) (acting during Tim Andrew's sabbatical) • Philip Wayne (2007–2015) • Annmarie McNaney (2015–present)
Facilities Between 1980 and 2010, there was an expansion of the school, including a new maths block, a textiles block, an art block, expansion of the English block, a new library and a new drama/psychology block. In 2015, the sixth form centre, located in the original building, was expanded and reopened as the Curtis Centre.
The Prime Minister's Global Fellowship Pupils attained places on the Prime Minister's Global Fellowship programme in the inaugural year 2008, and in 2009 had two more successful applicants. ==Admissions and school performance==