I think it basically comes down to the two-types of runners...Fast twitch v. Slow twitch.
A high schooler that is 'wired' to run 50-52 seconds for 400 meters and enjoys running distance will always have a leg-up on the kid who can't break 56 seconds to save his life.
BUT...that slow-twitch kid, if he's got the mentality and love for it, can certainly put in the miles and close the gap and in a lot of cases beat the fast-twitch kid.
I think with both types of athletes you need to have a great balance of high mileage (this is relative), leg speed development (year-round), and the proper amount of hard, race-specific training.
I tend to believe that the more you do something the better you become at it. So, the goal should be to run more from year to year. Freshman guys would run less than seniors in most cases. And with the idea of increasing your running (mileage) from year to year, you would increase your quality of work from year to year, etc.
If I coached high schoolers, or had a son that ran, and they came to me and wanted to be great at running and loved it and were passionate about it, I would have no issues with them building up over 4 years of high school to 80-100 miles per week in the off-season. They have to build up to it, they have to want to do that kind of mileage, and they need to have proper guidance of the whens and whys of what they are doing.