There is no max for anyone in terms of a one size fits all answer at any level. First, the mileage one person thrives on might be too much for another and not enough for yet another.
You need to keep in mind your own capabilities and add volume and intensity in a safe way especially in high school where you are still maturing. And differences in how boys and girls mature is another complicating factor.
Even if "we" say 70 mpw is the max. Well if you are doing 35 then are you going to double it starting tomorrow? That would not be a smart thing to do. Yes, it might work for a few, but the risk seems very, very high and not worth it.
Also more is not always better. There is a "breaking point" for each person. Finding that point is the challenge. Challenge seems like the wrong word instead we want to optimize the training to keep the runner healthy and enjoying running and then to optimize performance.
As for the type of training, well some longer stuff, some medium distance stuff, some low intensity (mostly) and then some higher intensity and then some even higher intensity.
There is another aspect to improving performance and that is rest and recovery. Get sleep, eat well, do some fun things.