I appreciate the response. So often the notion of non-school-affiliated running incites vitriol and fury. 'Pathetic' is often the term thrown out by today's youth. When I was that age, it would have likely been a slur fortunately unrepeatable today. At least you have reasons to discourage unattached running in some situations.
Point 2 first. This can be a real problem for the kid just starting out. How many pros tell a story of only being aware of the sport through the school program? I remember Beardsley's story of trying to play football but getting steered toward cross country (which he'd never heard of). However, the lack of alternative coaching isn't a huge issue in my mind. The guys I ran with were all uncoached but we had access to books. Lydiard was huge in those days, and Runner's World was for serious runners in the way that Running Times was later.
I don't believe I trained ideally but that is 20/20 hindsight. A lot of the reason I say that now is because of what has come to light since then, like the Italian school of which Canova is the most famous practitioner, and the internet which allows easy access to the theory. What I was doing at 15 didn't seem wrong at the time. These days especially, with widespread information sharing, there really isn't much question what to do. My school's coach wouldn't have had any idea what optimal 10km training looks like. He would have been far less effective than I was coaching myself.
Point 1. You are dead-on accurate here. Short of being at Lukas V's level of success (he never ran for his school's track team and perhaps never met the coach) running unattached makes you immune to scholarship offers. My peers and I were never planning to run in the NCAA and I made no attempt to do so. There are likely others like us today, but for all others, not participating in your school's program is a show stopper. Again, setting records and getting a ton of press (Athing Mu) makes you a hot recruitment commodity regardless, but for the masses, you better appear in State Meet results. I certainly never got a call from any college.
All that having been said, and I acknowledge your good points, not submitting to a laughably inept coach who is only 'your coach' because the school district hired him solves a lot of problems. Just look at the High School section of the Message Board once track is underway at schools across the country. These kids feel they are being underserved or even ruined by coaches. Especially if you feel your present and future are on the roads (10km and up) don't do yourself a disservice. Feel free to run the roads!