A Key Stage is a stage of the state education system in England, Wales, Northern Ireland and the British Territory of Gibraltar setting the educational knowledge expected of students at various ages. The term Key Stage is also used in Hong Kong although the ages at which each Key Stage applies differ from England.

The stages are as follows:

The National Curriculum sets out targets to be achieved in various subject areas at each of the Key Stages.

The Key Stages were first defined in 1988 Education Reform Act to accompany the first introduction of the National Curriculum. The precise definition of each of the main 4 Key Stages is age-related, incorporating all pupils of a particular age at the beginning of each academic year. The Key Stages were designed to fit with the most prevalent structures which had already grown up in the education system over the previous 100 years of development.

Key Stage 1 fits broadly with the first stage of primary education, often known as infant schools. This break had existed for some time, being acknowledged in the 1931 Hadow report as 'axiomatic' by as early as 1870.[1]

Key may refer to:

Stage or stages is an abstract object often associated with either theater and scene or point of progress.

It may also refer to:

Stage (theatre), a space for the performance of theatrical productions