had very similar PRs to you in HS. senior year ran 16:59, 4:28, and 9:55. mileage was around 45-55.
junior year i ran 2:05, 4:50, and 17 low. senior year i started doing indoor and ran 4:39, and then started dropping time a lot from training i did in the fall and winter -- got to 4:32, then 4:31, then 4:30, then 4:28.
first, try not to double unless you have a time conflict or something. singles are best at this mileage. you'll get much more benefit from longer runs than two shorter runs.
make sure you're doing strides too, 1-3x a week, at least 6x10-20sec of them at mile effort, and no more than 12.
bump up the long run. i started getting strong when i bumped my lr from 10 to 12-13. the kind of training you get in when you start to really roll at the end of a long run is unparalleled.
next, idk what year you're in but two weeks after your last track meet, GET TO WORK. bump up your mileage a little. use the summer to get strong. you can make it as simple or as complicated as you want, but try to build up to a threshold fartlek, a tempo, and a long run in your schedule. do lots of hills and strides. that's one aspect of my training in high school i regret not doing -- i never trained hard in the summer and took big seasons off for injury or no reason.