The series follows Keith Church (David Walliams), a socially naive chemistry teacher at the fictional Greybridge Secondary School, near Watford, North London, who falls for new French teacher Sarah Postern (Catherine Tate), who believes herself to be an inspirational teacher, in tune with youth culture and a beautiful woman. However she is also getting attention from arrogant and rude sports teacher Trevor Gunn (Philip Glenister).
Other staff members include Ms Baron (Frances de la Tour) as the alcoholic 'no nonsense' headteacher, Mr Martin (Daniel Rigby), a music teacher with ambitions to be a singer-songwriter, Mr Barber (Steve Speirs), a geography teacher who is having a nervous breakdown and is employed as a caretaker in the second series and Mr Hubble (James Greene), the elderly and confused head of science.
The pupils at the school are portrayed as being mainly interested in social networking, texting and partying and as being bored by the attempts of Mr Church and Miss Postern to engage with them. The most prominent of them in the first series is a streetwise pupil called Manyou, played by Joivan Wade, who is asked for advice on how to succeed with women by Mr Church.