it's for senior high school!! the k-12 thing is pretty recent and the addition of 2 more years of high school is pretty serious, kinda like college training, so most kids are going to universities already
shdjhff but actually before k-12 that was the norm, 16 yr olds already going to actual college, but the con with that is that some to most job applications in other countries would see it as an incomplete high school education, as well as other cons, so they changed the system to be k-12