All of the Above + Culture
The high 4 minute range is where talent, work ethic, and coaching all start to intersect.
A good coach can take a motivated kid of average talent into the 4:40s pretty easily.
A talented kid with poor work ethic can make it into the mid 4:40s pretty easily
A talented kid with a bad coach can make it into the 4:40's pretty easily.
To progress beyond the 4:40s, you need to have two of the three factors working for you. To be a really good high schooler, say sub 4:20, you need all 3 factors working for you.
Culture, which has only been briefly touched upon (soccer, xbox), is another factor. If the culture of your family, school, and town place value on running, you are going to have a greater chance of running fast. If the league which an athlete competes in is full of fast kids, the chances that your school will have fast kids goes up. Being surrounded by running success and being surrounded by people who work hard at running is a huge advantage when it comes to breaking past plateaus. I'll share a personal example from my coaching experience.
For many years, 5:00 was a heck of a benchmark for boys on my team. I would usually get 2-3 boys under 5, but not any more. This does not mean that I didn't have good runners, I had the #8 3200 girl in the U.S. in 2000 and have had plenty of boys place high in our section meet. Most of the rest of my team viewed those kids as outliers. The average joe on the team would say stuff like, "oh, yeah, Johnny. he is crazy". About 5 years ago, I set some performance bench marks for my track team. For the mile, the benchmark was 4:54 (which was based on the average final scorer at our league finals meet). Any kid who surpassed any benchmark would get a milkshake from the local diner and a t-shirt. Subsequent milkshakes and t-shirts could be earned by reaching higher and higher performance levels. It didn't take long for the kids who were hovering at the 5:05 level to realize that with a little more work, they could wear around one of the cool shirts, and get to have a milkshake while their teammates watched.
These days, we get about 5-6 kids under 5 per year (from a school of 750). Our fast kids haven't gotten much faster, but the # of kids willing to work hard has gone way up. What started as kids shooting for a goal so they could get a milkshake, has translated into a team wide culture of running on the weekends, running during the off season, and even running in the morning. So, we are getting more of the average to slightly above average kids to put in the work and we are seeing them end up in the high 4 minute range as a result.