Wiktionary
k-12
abbr. (context North America education English) kindergarten through 12th grade (US)/grade 12 (Canada).
Wikipedia
K-12 (Kansas highway)
K-12 was a state highway in the U.S. state of Kansas, created in the mid-1980s. Its alignment was changed during its existence.
Usage examples of "k-12".
Someday, perhaps half of our K-12 education will be psychological--understanding ourselves and others, developing a philosophy of life, controlling our emotions and behavior, learning to find and give love, caring for all people, animals, and the earth (see chapter 1).