A preparatory school, or prep school in the United Kingdom, and previously in the British Empire and so the Commonwealth in current English usage, is an independent school designed to prepare a student for fee-paying, secondary independent school (public school). Whilst many prep schools prepare their students for entry to a range of senior schools, some are closely associated with a single school.

Traditionally Prep Schools are for eight to thirteen year olds, when they take the 13+ Common Entrance examination for entry into a Public School; to run parallel to the state system, many Prep Schools now run until eleven, and the senior schools from eleven. This is particularly the case in day schools and girls' schools, whereas the traditional boarding schools still run from 13 to 18. Under the age of eight, students are educated at a "pre-prep" school, which takes the place of a state primary school.

Thus, independently educated boys will typically go to a pre-prep school from ages 4/5 to 8, to a prep school from age 8 to 13, and to a public school 13 to age 18.

Girls' private schools in England tend to follow the age ranges of state schools more closely than those for boys. Thus, a preparatory school for girls will usually take students from age 5 to 11, and independent schools for girls after prep school will usually begin at age 11 and continue to age 18, with no age 13 intake.