Not running higher mileage in high school is one of my biggest regrets as a (female) runner.
Not just because I think it would have made me a better runner sooner, but because I had a terrible transition to running in college. Almost all my female teammates who had successful college careers ran considerably more mileage than I did in high school (not necessarily high mileage but at least 40-50 mpw), and had considerably less difficulty adjusting to college level training.
I wasn't unmotivated, I trusted my coach and his training plan. That's not necessarily a bad thing, but he had the stupid idea that more than 25 mpw was too much for girls and he actually told us not to run more than that over the summer. I'm sure that going from 25 to 40 miles over 4 years would have been better than trying to do that over the summer before college.