| St. Nicholas Grammar School for Boys | |
| Coordinates: | 51.5948°N -0.4137°W |
| Established: | 1955 |
| Closed: | 1977 |
| Type: | State grammar school |
| Head Label: | Headmasters |
| Head: | RFE Watson (1955) LE Shearn (1976) |
| Address: | Wiltshire Lane |
| Country: | England |
| Postcode: | HA5 2LX |
| Local Authority: | Hillingdon |
| Ofsted: | no |
| Staff: | 40-45 (full-time) |
| Enrolment: | 650 students |
| Gender: | Male |
| Lower Age: | 11 |
| Upper Age: | 18 |
| Houses: | Abbots, Kevere, Bec, Kings |
| Colours: | Purple and Gold |
| Publication: | St.Nicholas School Magazine (annually) |
| Website: | https://www.sngs.org.uk |
St Nicholas Grammar School was a grammar school, located in Northwood Hills, in the London Borough of Hillingdon, Middlesex. In 1977, it joined with the neighbouring St. Mary's Grammar School for Girls to form Haydon School.
Approval to begin construction of St Nicholas Grammar School was granted on 11 May 1953, and the work was undertaken by the construction firm of Holland, Hannen & Cubitts.
In 1954, two forms were established at Bourne Secondary Modern to become the nucleus of pupils, forming 2a and 2b at the new building in 1955.
The grammar school opened in 1955, and ran for 22 years. Its crest was a bishop's mitre surrounded by three money bags. The first headmaster was Dr. Robert Watson (8 March 1910 - 16 July 2004), who assembled the teaching staff during the late winter and early spring of 1955. He held the position until retiring at the end of term 1975.
Robert Watson was succeeded by Leslie Shearn who guided the school through amalgamation with the adjacent girls' school. In 1978, Haydon School changed the crest to a stylized stag's head.
There were four houses; each with its own staff. Abbotts, which was red, Bec, which was yellow, Kevere, which was green, and Kings, which was blue. The houses were named after local landowners: Abbots was named after the Abbots of Bec, who owned the Abbey of Bec and its estates from about 1090. Two abbots became Archbishops of Canterbury. A later Abbot, Gundulf, was responsible for the building of the keep of the Tower of London. Bec house was named after the Abbey of St Mary Bec, founded in about 1040. Its connections with the area began about 1090 when one Ernulf of Hesdin left all his lands, including the manor of Ruislip, to the abbey. The estate was managed by the prior of Ogbourne who owed allegiance to the Abbot of Bec.
A House Assembly was held once per week, on Friday. Each house had its own colours. There were many inter-house competitions throughout the school year, the emphasis being on field sports, though there were also drama, chess and art competitions.
There was a language laboratory, senior and junior science laboratories for chemistry and physics, a school orchestra, a library, workshops for metalwork and woodwork, and several pitches for games. The playing field was shared with St. Mary's Grammar School for Girls.