In my neck of the woods, an LPN course of study is offered in vocational/technical high schools. (along with hairdressing, auto mechanic, building trades, culinary arts...). It is a non-tradtional high school.
One week of nursing classes, the next of clinicals. Add that to 2 years, (which is one's jr. and sr. year of high school) and it equals out to what a technical school will teach adults seeking an LPN diploma full time. (freshman and sophmore years, they complete their traditional educational requirements, taking the "CAS" tests state required for graduation.
After year 1, it (Jr year) it qualifies a student be certified as a CNA. (which is far longer than someone who takes just a CNA course). Clinicals and nursing courses in year 2 (senior year) means that they qualify for the NCLEX. No one can sit for the NCLEX PN without having a certain state mandated number of clinical hours/classroom hours. The only thing that can happen is that if a student is 17 at the time of the end of senior year, and clinicals require you to be 18, they need to continue with clinical rotations after high school until the requirement is met.
Many, many communities have vocational/technical high schools. They are aimed at a non-traditional student whose choice is not a college prep situation. Each state is set up differently, as is each school. As are course offerings. As an adult, I went to a vocational school for my LPN. I took the same course as the high school kids did during the day. The school I attended had a number of vocational choices. Many chose to work as an LPN, a CNA, a mechanic, an electrician, then pursued college, advanced certifications, that type of thing.
I wish I was in an area when I could have done this in high school, as I would have most certainly been able to pay my way through college by working before life got in the way.