The School is situated on the Sackville estate, on grounds bordering the park of Knole House. It is the venue for the Thomas Trophy, an annual cross-country running event which attracts nearly one thousand competitors from schools across South-east England.
There is some uncertainty about the very beginnings of Sevenoaks Preparatory School, but tradition has it that in 1919 Mrs Garrod, wife of the headmaster of Sevenoaks Grammar School, (now Sevenoaks School) brought together a class of six boys who were too young to attend the main school. She educated them herself in the Grammar School Cottage Block until they were ready to move up.
In 1921 the Rev C G Holland became head master of an already expanding prep school. He bought No. 4 Vine Court Road, to be known as Old School House, and moved there with thirty five boys. The back garden on two levels became the playground, known from then on as the upper and lower Quad. Education consisted of Latin, divinity, arithmetic, history, geography, English, French but no science. There was art, and drama with an annual school play on the lawn, singing and music, and some sport on The Vine Cricket Club Ground and Hollybush Lane Recreation Ground. Gym was mainly marching and turning conducted by an ex-Army Sergeant Major. School caps, which were then maroon and black, were worn as a badge of honour and defended in many sore contests.
In 1928 Mr M N Jukes, MA, a wounded veteran of the Gallipoli campaign, bought the school, inheriting thirty boys. He took in a few fatherless boys, as boarders and cared for them like sons. By 1931 there were seventy two pupils and by 1938 one hundred and two. In this year Mr F G Morgan became joint headmaster. Having survived two World Wars Mr Jukes fell a victim to increasing road traffic. Mr Morgan having moved on in 1946, in 1947 Mr Jukes was seriously disabled when knocked down by a car. From then until his death in 1957 Mr Jukes continued to supervise the school and even teach from his bed, while his able assistant teacher, Mrs A E Lang MA, became headmistress. She maintained the school with all its high reputation until it was bought by Mr K C Ely in 1958.
For ten years Mr K C Ely developed the school to meet the increasing demands of education. Averaging between a hundred and forty and a hundred and fifty boys between the ages of five and fourteen on the register, he hired the Carey Hall of the Vine Baptist Church. Anxious for room to expand and, in particular, to have grounds and playing fields for his boys, Mr Ely took up the tenancy of Fawke Cottage at Godden Green, part of the Sackville estate in the grounds of Knole House.
In 1978 Mr Ely retired, handing the school on to Mr E Oatley, who came from his post as deputy head at Winchester House. In 1986 the school took over the lease of the adjacent Stake Farm as a base for the Pre-prep department. The playing fields were greatly extended, with athletics track, floodlit seven-a-side pitch and all-weather cricket nets. In 1987 a larger car park was built and a new Reception block was put up in the back garden of Stake Farm to enable the school to run two classes in each year group. Considerable expansion took place in the early years of the 21st century with numbers reaching nearly 400 pupils. A large modern sports hall was opened in the millennium year, this being followed by a new classroom block. On his retirement in 2005 Edward Oatley was honoured as a Member of the Order of the British Empire (MBE) for services to education and to the community in Kent.
The present head of 'The Prep' is Mr Philip Oldroyd. Mr Oldroyd is one of five former pupils of the school who are currently members of the teaching staff.