Its origins date to 1908, when Sleaford Council School opened at Church Lane to meet the growing demand for elementary education in the town.

The conversion included a government grant of £20 million to carry out extensive building work on both sites, completed in 2012 at Sleaford and in 2015 at Ruskington.

Pupils generally sit examinations for General Certificate of Secondary Education (GCSE) or equivalent vocational qualifications in Year Eleven (aged 15–16), and they have a choice of three or four A-levels or vocational options in the sixth form, which is part of the Sleaford Joint Sixth Form consortium with the town's single-sex grammar schools.

In 2019, the school received an "average" Progress 8 score; 31% of pupils achieved English and mathematics GCSEs at grade 5 or above, which was lower than the national figure.

An Office for Standards in Education, Children's Services and Skills (Ofsted) inspection in 2015 graded St George's Academy as "good" in every category.

[13] The Board of Education sanctioned these changes on the condition that new classrooms be added to the Council school to accommodate Senior pupils and a new Infants' department be erected at the site.

Instead, HORSA huts at the site were acquired for the still-mixed Sleaford Secondary Modern School;[21] teaching took place there during the 1950s and new classrooms were added during the decade.

[26] This was the first phase of a proposed building programme which would have built a whole new school on the Westholme site with an enlarged assembly hall, a library, gymnasium and classrooms capable of accommodating 750 pupils across five forms (year groups), fulfilling the council's ambition to consolidate the secondary modern onto the Westholme site (the old HORSA huts would have also been demolished).

[27] While the plans were approved locally, central government funding for the next phase of development at Westholme was indefinitely paused in the early 1960s, leaving the dual school system in place.

[28][29] A reluctance to improve secondary moderns or expand grammar schools under the Conservatives prompted the Labour Government to issue Circular 10/65 in 1965 which requested local education authorities convert to a comprehensive system.

[38] In 1974, staff wrote a highly critical letter to the county council concerning the poor standard of facilities at the school, noting its split-site, aging temporary accommodation and Edwardian Church Lane site.

They noted that: "there have been several attempts ... to arrive at a suitable scheme for comprehensive education in the area, none of them so far put into operation ... we feel that we have waited too long for ... something more positive [to be done] about our accommodation problems.

[57][58] To commemorate the new buildings and the end of the dual-site format, the Board of Governors voted to adopt a new name: St George's School, which came into effect from September 1984.

[75] Despite a delay in 2008,[85] the scheme was revived the following year: the three remaining schools would merge and up to £40 million of funds were being considered to pay for the redevelopment of each site.

[87] A feasibility report indicated that Aveland was not sustainable due to falling enrolment and would have to close; instead the remaining two sites would be redeveloped with £20 million of Government funding.

[103] Upon admission, pupils are allocated a mixed ability form, where they are registered, taught Life Skills and have access to pastoral support from their tutors.

[102] Before the conversion to Academy status, the school uniform consisted of a navy-blue blazer with the school emblem sewn on, a white shirt, navy-blue tie and dark-grey trousers (girls could wear plain-blue skirts) for all pupils in years 7–10; year 11 pupils could wear a dark-blue jumper, shirt and grey trousers.

Although morning assemblies take place and are Christian in nature, they are non-denominational; in some cases, local clergy attend as guest speakers.

[117] In Key Stage 4 (Years 10 and 11), pupils study a core curriculum comprising English, mathematics, science, PE, RE and citizenship.

[120] The Joint Sixth Form allows pupils to choose from around 60 vocational or academic subjects including: A-Levels in biology; chemistry; computing; design engineering; drama; English language and/or literature; French; history; geography; German; fashion and textiles; law; mathematics; further mathematics; media studies; philosophy, ethics and religion; photography; physical education; physics; product design; psychology; sociology and Spanish.

The score for St George's Academy in 2019 was "average" (-0.03, with a confidence interval between -0.17 and 0.1),[122] meaning that pupils do about as well as those with similar previous attainment nationally.

[136] The physical education department runs Inter-House sports competitions and co-ordinates school rugby, association football, basketball, boccia and netball teams.

The school building had entrances for girls and boys, who were taught separately in six classrooms; the assembly hall was 62 by 28 feet (18.9 by 8.5 m) with a domed ceiling.

[144] Initially occupied by Kirk's business partner Thomas Parry,[144] the businessman and Liberal politician Samuel Pattinson lived at the house from at least 1924 until his death in 1942.

[153] Two years later, the school acquired the adjoining Westholme Lodge for use as a space for girls to practice domestic science,[23] and in 1959 a sports pavilion opened on the site.

[26] These plans were submitted to the Ministry of Education for the 1964–65 year,[155] but central government funding was paused indefinitely[26] and teaching continued to take place between the existing buildings at Westholme and those at the Church Lane premises.

[57][58] Fitted with a satellite dish that could pick up signals from Russia, the centre housed a computer laboratory and classrooms; a local reporter described it as "probably the most advanced in the country" at the time its designs were released to the public.

[163] To accommodate a rising school-age population, the school asked in 2020 for permission from the local planning authority to construct five new classrooms and extend the existing music block with the addition of a new floor.

[164] In 2016, the Board of Governors announced plans for the construction of a swimming pool and fitness suite at a cost of £3.7 million to be paid for using the Academy's 'capital reserves'.

[170] Built on a 9-acre (3.6 ha) site at a cost of £100,658, the new school buildings consisted of a three-storeys of classrooms and a gymnasium, assembly/dining hall, library and greenhouse.