No, it’s just a title. Directional State University will have professors because they have a status hierarchy and titles are a significant part of that, and the total compensation.
As I understand the US system for four year universities
TOP
Professor with an endowed chair
University or Full Professor
Associate Professor (They have tenure and time in position)
Assistant Professor (They don’t have tenure. This is their first job and they want tenure here.)
BOTTOM
Visiting Assistant Professor (They got denied tenure at a higher ranked university than they currently teach at and want tenure at that university or another one of similar rank.)
Adjunct Professor
Someone with a non-academic job, expertise or position who teaches a university course because they enjoy doing so. Also a deluded holder of a Ph.D. who thinks this is still a part of academia. It is not. That is why it is below the bottom. These people are highly qualified, poorly compensated casual labour, desperately clinging to hope of an academic career after this makes any sense.
Your characterization of adjuncts is unnecessarily harsh. Many simply enjoy teaching in a university environment and aren't "desperately clinging" to anything.
Adjunct lecturing has terrible working conditions and benefits. It is a hobby, not a job. No one should do it as a job. Anyone who treats it as a job should be dissuaded from doing so as forcefully as possible to prevent further suffering. If you have a spouse with a good job and insurance or a trust fund by all means do it as a hobby, even an especially engrossing one.
Anyone who describes themself as an adjunct professor as if it’s sonetbing other than a hobby should be encouraged to get a job that isn’t shit. Teaching high school is vastly less intellectually rewarding but the holidays are better and so is the insurance and the pension.
I looked into this in my state. Getting your foot in the door as a teacher in a public school would require someone with a PhD in say, mathematics, physics or computer science, to go back to grad school for a masters in education. Not sure that's an option, and is also ridiculous considering I just spent six years in grad school. You could do TFA as a backdoor, in many states, but that is probably an even worse deal for you physically and emotionally than being an adjunct.
I’m not saying it’s a good deal for anyone capable of getting a doctorate. It’s clearly superior to being an adjunct though. They’re low paid, insecure, highly qualified labour. Once you have a doctorate and you have two years on the job market without a tenure track job you’re done. You’re never getting a tenure track job and you’re better off getting the he’ll out. There are some exceptions but assuming you’ll beat the odds is a losing bet. Even those two years of adjuncting, doing teaching and research and hoping is a losing bet but it’s not an insane, fallacious waste. Sometimes people make it out. For all practical purposes no one makes it to tenured Professor, of whatever rank, after two years adjuncting.
Many states have backdoors that are regularly used to hire exceptional non-traditional candidates such as practicing Lawyers, experienced Engineers, and science/engineering PhDs (even PhDs in the humanities if the PhD is from a prestigious name).
But you need to get your resume in front of the right people -- namely, folks in the central office (or maybe principals) who view your area as a strategic/difficult hiring area. Easy peasy in CS these days...
My understanding is that private (k-12) schools pay dramatically less than (unionized) public schools. I've had family and friends who taught even at very expensive secular private schools, who then moved over to public school because the pay, pension and benefits were dramatically better.
I don't have hard numbers, but my impression from talking with family and friends is that you are much better off as an adjunct at a public college than as a k-12 teacher at even a prestigious private school or non-union charter school, though a union teaching job at a public k-12 school pays better and is much more stable than both.
In my experience, visiting assistant professors are often freshly-minted PhDs building up their portfolios before going on the job market “for real.” It’s like a postdoc but with much more emphasis on teaching.
As I understand the US system for four year universities
TOP Professor with an endowed chair University or Full Professor
Associate Professor (They have tenure and time in position)
Assistant Professor (They don’t have tenure. This is their first job and they want tenure here.)
BOTTOM Visiting Assistant Professor (They got denied tenure at a higher ranked university than they currently teach at and want tenure at that university or another one of similar rank.)
Adjunct Professor Someone with a non-academic job, expertise or position who teaches a university course because they enjoy doing so. Also a deluded holder of a Ph.D. who thinks this is still a part of academia. It is not. That is why it is below the bottom. These people are highly qualified, poorly compensated casual labour, desperately clinging to hope of an academic career after this makes any sense.