Preschool and kindergarten are both early childhood education programs that prepare children for their future education. Preschool is a broad term that can describe programs for children between the ages of 2 and 5 years old. Pre-K, on the other hand, is for older preschoolers who are getting ready to attend Transitional Kindergarten (TK) or Kindergarten in the next year. TK is specifically for kids who turn 5 between September and December.

In California, children who will be five years of age on or before September 1 are eligible to attend kindergarten. Children who turn five after December 2nd of the school year will have to wait to enroll in kindergarten the following school year.

To summarize, preschool can start as early as 2 years and 6 months old, while Pre-K is typically for 4-5 year old children, and TK is specifically for kids who turn 5 between September and December. Kindergarten is available to children whose fifth birthdays are on or before September 1st of the school year.