As someone who went to a small high school in Ohio and had no real competition until the regional meet usually I can probably weigh in on this.
For example my mile PR from high school occured in our conference meet in which I won by 13 seconds. My 2 mile PR was set in a dual meet where I lapped second place. I later went to an invitational with several larger schools and beat my 2 mile PR so that tends to agree with some other comments you've received.
I just tried to lock in on a race plan. Some weeks in the mile I'd go out slow through half way and work on kicking as hard as possible from 800 out, other weeks I'd go out way too fast and challenge myself to hold on. I even had one where I tried to race like Chelimo for a 2 mile and throw in random surges every other lap. Just try to prepare yourself for the bigger races. I also prided myself on trying to push myself hard enough to have a chance at a PR whether I had competition or not. I certainly am not a world record holder or an All-American, just an above average guy who had an average D1 college career but wasn't challenged in high school. Believe in yourself and push your limits. A solo effort race is better than any workout your coach will throw at you.