What is "pre-kindergarten"

Pre-kindergarten (also called Pre-K or PK) is a classroom-based preschool program for children below the age of five in the United States, Canada and Turkey (when kindergarten starts). It may be delivered through a preschool or within a reception year in elementary school. Pre-kindergartens play an important role in early childhood education. They have existed in the US since 1922, normally run by private organizations. The U.S. Head Start program, the country's first federally funded pre-kindergarten program, was founded in 1967. This attempts to prepare children (especially disadvantaged children) to succeed in school.