A preparatory school, also known as a college-preparatory school or prep school, is a type of secondary school that is primarily designed to prepare students for higher education. The term "prep school" is short for "college preparatory school". These schools can be public, private independent, or parochial.

Preparatory schools began before the Civil War in the United States when there were no public schools above the grammar school or elementary level. Graduates of these schools were not ready for college study, so many colleges set up "preparatory academies" to prepare them for college study. The preparatory division could dwarf the college enrollment, as at New York Central College. There were also preparatory schools unaffiliated with colleges, especially for girls, such as the Columbia Female Academy.

Today, preparatory schools are primarily private, elite institutions that have very selective admission criteria and high tuition fees, catering to students in the 13–18 age range. Little financial aid other than loans is available. Public and charter college preparatory schools are typically connected to a local school district and draw from the entire district instead of the closest school zone. Some offer specialized courses or curricula that prepare students for a specific field of study. In contrast, others use the label as a promotional tool without offering programs different from a conventional high school.

The benefits of attending a preparatory school include college preparedness, as these institutions are focused on preparing students for higher education. The lessons learned, classes taken, skills developed, and achievements made can make students more competitive in the college application process. However, not every high school prioritizes college preparedness in its curriculum and approach.

It is important to note that the term "college preparatory" can be used by schools as a promotional tool without offering programs different from a conventional high school. Therefore, parents should evaluate a schools actual programs and curriculum rather than relying solely on the label.