K-12 is an English language expression that refers to the range of years of publicly supported primary and secondary education found in the United States and Canada. The term "K-12" is a shortening of kindergarten (K) for 5-6 year-olds through twelfth grade (12) for 17-18 year-olds, as the first and last grades, respectively, of free education 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.

K-12 schools are usually divided into three levels: elementary school (grades K-5), middle school or junior high school (grades 6-8), and high school (grades 9-12) . In some instances, these three groups are kept separate; in others, elementary and middle school are grouped together, but high school is kept separate. In other cases, all levels are held together on the same campus.

K-12 education is the foundation of a students academic career and provides the basic knowledge and skills necessary for success in college and the workplace. K-12 education also plays an important role in developing responsible citizens and preparing young people for the challenges of adulthood. Benefits of a K-12 education include academic preparation for college and the workforce, social and emotional development, exposure to different cultures and perspectives, and opportunities for physical activity and extracurricular involvement.

K-12 education is free in the U.S., with most schools being public. However, there are also private K-12 schools that serve all 50 states and international students. Laws regarding compulsory education vary by state, and they address starting and ending ages, as well as the level of participation.