Complex sentence: Pre-kindergarten (also called Pre-K or PK) is a classroom-based preschool program for children below the age of six in the USA, which may be delivered through a preschool or within a reception year in Elementary school.
Split into simpler sentences: Pre-kindergarten (also called Pre-K or PK) is a classroom-based preschool program for children below the age of six in the United States. It may be delivered through a preschool or within a reception year in elementary school.