I don't know about junior high girls but Jenks does have an 8th grade boy who ran the mile in 5:02 at the last cross country meet, haha.
The mile only teaches you to pace and run at a speed you won't on the court.
We have a kid who can run a 5:00 flat mile but when you run shorter distances with short rest time, he is usually in the back of the pack.
It is fine to use as a measuring stick for pretest and post test, otherwise it really is pointless.
I am willing to bet they only do this to get a time.