The school attracts students from not only the town of Caistor, but also several surrounding settlements, including Grimsby, Brigg and Market Rasen.

In the 2017 Times newspaper league tables it is in the top ten mixed state schools in the country.

The Dissolution of the Monasteries in the reign of Henry VIII had destroyed the principal sources of education of the times, and the numerous schools endowed throughout England during the following reigns are evidence that public-spirited men recognised the need created and endeavoured to meet it.

Among others was Francis Rawlinson, of South Kelsey, who died in 1630, bequeathing money to endow a school at Caistor, and William Hansard of Biscathorpe, who supplemented the original gift in 1634.

The monies given were invested in the purchase of land at Cumberworth, and of the rectorial tithes of Bilsby, of which the governors are still lay impropriators.

On 18 February 1960 fifty-two boys and girls at the schools walked the twenty six miles to Lincoln.

The school occupies a site close to the centre of the small market town of Caistor, with remarkably steep topography.

[10] The school previously owned several other buildings in Caistor, including the "Red House" next to Bank Lane, which were used as boarding accommodation.

In 2010, as part of the Government Building Schools for the Future scheme, Caistor Grammar School secured funding to build an extension to Lindsey House, to provide renovated music facilities, another ICT facility and a room for food technology, something that is new to the CGS curriculum.

In 2013, a new science building was constructed adjacent to Lindsey House, named the Olympic Torch Building to honour the five CGS pupils who carried the torch for the London 2012 Olympic Games, as well as Jordan Duckitt, one of the seven young athletes to light the cauldron.

The building was opened in September 2013 by UK Sport chair Baroness Sue Campbell.

This new "New Hall" has PV cells, an air source heat pump and insulation (the new hall was noted by staff and student alike that it was incredibly cold and hot, weather dependant, and that the small heating element was not very effective).

Pupils are taught a variety of traditional subjects and modern languages remain compulsory to GCSE level.