I am 15 years old and my PR (got it yesterday) is 21:11. This season is almost ending and I hope to break 20 this season.
To me, I think mile repeat helped me the most. Coach put people in a certain group with a certain time to beat. I was put in the 6:30 group. The place that we did mile repeat was pretty hilly too. so we do one lap(1 mile) under 6:30, then two min rest then another one, then another one. If anyone in the group didn’t make the mile under 6:30 we all ran the 4th one but this time 30 seconds added to the time tha you originally had to beat.