The school grounds occupy approximately 250 acres (100 ha), and the oldest buildings date from the late 16th century.

The school was founded in 1583 by Edmund Grindal, Archbishop of Canterbury, who was born in St Bees, at Cross Hill House.

Thanks to an agreement with Queen's College Oxford and the purchase of local tithes, the school prospered both financially and academically.

In 1842, compensation was paid by the Lowthers which was used to build the present open quadrangle, which includes the original schoolhouse.

By 1900, the school's chapel, additional classrooms, library, swimming baths, Gymnasium, science labs, and lecture theater had been built.

One hundred and eighty boys and staff died during the war, and a memorial was built overlooking the sports fields where so many had previously played.

[9] Help was at hand, but during the Second World War, Mill Hill School was evacuated to St Bees after their buildings were occupied by the government.

[10] The cadet corps of the two schools combined with village volunteers to form the St Bees Home Guard.

It was a multi-function business centre and teaching area, which was named after the then chairman of the board of Governors, William Whitelaw, sometime Deputy Prime Minister of the United Kingdom.

In September 2008, a Preparatory Department was launched, catering for pupils from the age of 8 until they joined the main school.

"[16] On 20 March 2017, it was announced that the school would re-open in partnership with Full Circle Education Group after refurbishment.

[19] One of the aims of St Bees is to provide an opportunity for pupils to appreciate the arts as well as to experience the benefit of time on stage and behind the scenes.

[22] Notable Old St. Beghains include two Vice-Chancellors of the University of Cambridge, a number of professors, and three Victoria Cross recipients.