I like what you said about 'managed expectations'--and I think I agree with both sides of what you said. Publishing is incredibly tough, not just in finding someone who wants to publish your work, but also in the enormous amount of work it takes to rework and rework to bring it up to a publishable state. As you said, most writers will need to expect to be working on their writing for years before publication. That being said, I think some kids do have a gift, and if they are capable of producing a work of a publishable quality (and have the discipline to see it through, or have people they are collaborating with that can help), then it doesn't seem like there should be any reason why it should be rejected out of hand just because of age.
Again, I like what you said about managed expectations, because I think that's a big part of what's at issue here. There's a fine line to navigate; I think most educators and parents would like to encourage kids to write more, and see them self-motivated to work on their writing skills (kids really do learn so much faster when they put time into something of their own volition), and there's nothing wrong with dreaming of being published, but at the same time, the last thing you want is for young aspiring writers to become disillusioned by a bad experience of trying too hard to get published, maybe before their skills had developed enough to be ready for it.
I will say that in my experience, (especially reading a variety of stories on fanfiction.net) mine has been similar to yours in that older writers seem more often to produce higher quality work, for the reasons that you stated above, that they have more experience in the world and in writing that allows them to put to use various writing techniques and write more believable dialogue, create better characters, etc. Particularly I can see in myself in my own writing journey the incredible difference between what I was writing when I was fifteen, and what I'm writing now ten years later. A lot of that was indeed related to my lack of experience in the world, characters not acting believably in a given situation and so on, but even though my writing has improved quite a bit, part of becoming more experienced as a writer has made me far more aware of how much room there is for improvement.
But anyway, thanks for sharing your thoughts, I definitely agree with what you say. I think for topics like this, a simple yes or no answer really isn't sufficient; there's so much more you have to think about. (Oh, and you've had technical papers published, eh? Don't suppose these are available anywhere online to read. (; Not that I would probably be able to understand them anyway, lol, but...I am curious. (; )
Oh, I'd like to address one or two things said earlier on in this thread (and yes, I guess it was several years ago X3), particularly concerning the idea that young writers who believe they'll have no trouble getting published are 'arrogant.' I think it's important to remember that it's a good rule of thumb to expect that, as the author, you won't be able to see your own work clearly, at least not for a while. Very often readers seeing your work for the first time will immediately pick out errors or places of believability breakdown that are invisible to you (sometimes even when they are directly pointed out), and as far as I've been able to tell, this experience is nearly universal. You almost can't help but believe that your writing is very good, particularly when you are in the moment of writing it—and that makes sense, because if you didn't like what you were writing or think it was good, you probably wouldn't be able to find the motivation to write it. I know I experienced that when I had only really been writing a few months; I started out hyper self-conscious about my writing, but after a while I naturally began to build up more confidence, and though I did my best to temper the feeling, I really did feel as though the quality was getting close to on par with some of my fanfictions heroes of the time. (Which for me, was basically the equivalent of thinking my work was worthy of publication.) Now I look over my older writing, and I can see exactly what its flaws are (and why it didn't get close to the number of reviews of my favorite fanfictions XD).
Again, I believe this is something most authors (especially inexperienced authors, but even experienced authors can fall into the trap too) experience, and I'm uncomfortable applying such condemning terms as arrogant to describe it. For the same reason that a younger writer is often going to have a harder time writing believable characters and situations, a young writer (such as I was at fifteen) is likely going to have trouble seeing their own writing clearly, and have an understanding of just how difficult writing is, or the surrounding context of just how difficult it is to get published. Just like it's taken time for my writing style to develop (and stop putting question marks at the end of every sentence...yeah, that was one of my early habits that lasted way too long), it's also taken time for my awareness in my own writing flaws (and how my writing really compares to others) to develop, too. My older work was flawed in many ways for a variety of reasons, but I respect the amount of time and effort my old self put into it, as I would any young aspiring author, and I understand that not only technical improvement, but general awareness of how others will see my writing, requires time and space to get better.
[Vaguely related tangent: Awareness is important, I think, but you can end up going to the opposite extreme too. What I've been battling lately is the state of being hyper-aware, the point where you start looking at other published work you see and constantly feel overwhelmed by your own work's inferiority. I've found for my writing that I need to have on standby at least two states of mind: the inspired, almost unrealistically confident, everyone-is-going-to-love-this state, which I need to be able to grind out new material, and the harshly critical one, which is skeptical, and goes over every single detail hunting for areas of unbelievability or inconsistency. I really need both, but often the second mind will try to take over too much, and at that point I get completely stymied. I've almost started to think that you need to be overconfident at times if you're going to write. But of course, you also have to be able to step back, or, as you said before, you can find yourself disappointed.]
So, anyway, those are my thoughts on that subject, lol. (I definitely think it is important to help people, not just kids, understand how difficult it is to get published, and the work involved, but I think there are ways to get this across without the use of alienating or condescending language. There are indeed writers out there who won't accept any criticism or have any interest in improving, but there's very little to be done about that, and I think often many writers are more open to critiques than they might seem at first, so long as the criticism is phrased in a way that respects the work and the time and effort put into it.)
150 pages? That's impressive. (Writing really is tough work, and just putting in the effort of writing that much takes dedication and a real love of what you're doing. I admit, I always wanted to write as a kid, but I just never could get myself to sit down and do it, and I didn't really start writing until I was fifteen or so. Looking back, I think that set me back in terms of my growth as a writer. That's awesome, keep going!)
*...And, I'm back to my obscenely long, this-post-was-originally-twice-as-long-but-I-tried-to-cut-back posts. X3 (I thought after that 7,000-word post in 'How do you rank the books' I was going to cure myself, but apparently not. This is the problem in my fictional writing too. I try to include every possible thing, and the coherency and sense of purpose completely breaks down. X3) Oh well.
“After all, absolutely no one can help but suspect a criminal, liar, and manipulator of committing crimes, lying, and manipulating. And of course, no one is more aware of that simple fact than Artemis Fowl.”
Opal sets into motion her most diabolical scheme yet, to frame Artemis and turn his closest friends against him. Only this time she has a new calculating partner who knows Artemis better than he knows himself. [An Artemis Fowl fanfiction, set after The Atlantic Complex.] https://www.fanfiction.net/s/8336552/1/Noble-Heart
...Shameless self-advertising, guys! C;
(And if you're really bored: http://axxonu.deviantart.com/gallery/28912232/Artemis-Fowl
AF fanart. ;J)