My question is as stated in the title, when do you know to switch the focus of a 400 runner to becoming an 800 runner, specifically at the high school level. To be a top-level 800 runner, you need pretty good 400 speed. These types of runners are rather competitive on the high school scene and it is difficult to take that success away from them for the unknown of a new event. Obviously, running these events are not mutually exclusive but training should be a little different. I have my ideas, but was curious about what others thought/have done in the past.