High Quality Content by WIKIPEDIA articles! Pre-kindergarten (also called Pre-K or PK) refers to the first formal academic classroom-based learning environment that a child customarily attends in the United States. It begins between the ages of 3-5 depending on the length of the program. It was created to prepare students for a more didactic and academically intensive kindergarten and is the traditional "first" class that school children participate in. Pre-kindergarten is not required. On the other hand, it acts as a way to prepare children (especially those of a disadvantaged population) to better succeed in a kindergarten (often compulsory in many U.S. states). Pre-kindergarten was also known as nursery school, but the term was phased out during the 1990s.