Lambrook is an independent preparatory school for 615 boys and girls, aged 3–13, set in 52 acres (21 ha) of Berkshire countryside.

Major expansions of the premises took place between 1978 and 1984 during the headmastership of Tom Clough, including a new teaching block, a squash court and an all-weather pitch.

During this period the school gained an outstanding reputation for the high calibre of teaching and the academic and sporting achievements of its pupils.

[5] Lambrook declined under the tenure of Michael Bickersteth (1989–92), with numbers dropping considerably, a trend not significantly changed by his successor Robin Badham Thornhill, who resigned in 1997 to take up the Headship of Summerfields, Oxford.

In that year the Governors approved a merger with Haileybury Junior School in Windsor which was beset by the limitations of its site, and John Hare, headmaster of Haileybury was appointed to the new combined school, called Lambrook-Haileybury, with 200 children, now of both sexes, both boarders and day pupils.