The expression "K-12" is a shortening of kindergarten (K) for 4- to 6-year-olds through twelfth grade (12) for 17- to 19-year-olds, as the first and last grades, respectively, of free education[6] in these countries. The related term "P–12" is also occasionally used in Australia and the United States to refer to the sum of K–12 plus preschool education.[7][8]