Ernie has done this sucessfully for a long time so follow his advice and spend a lot of mental effort on choosing the best possible location. Like retailing (another case where location is important) there isn't a single perfect location and what you have to decide is what is the best spot for the event, your equipment capabilities, and what you most want to capture from that event.
Lens reach really factors in with high school low light shooting. If you have to severely crop an image captured in low light, the noise becomes much more obvious but more problematic to me is the loss of overall image quality and effective resolution as you take a severe crop from a camera being used at high ISO.
For example below are a couple of ISO 20,000 shots from the first game I shot with my 1DX 2 last year. The first is a quick capture that our star keeper asked me to grab for her social media account before the game and that image is the full frame, the second image is at the same ISO but cropped from about 12% of the frame from an overall post-game image. The first is fine for her social media use, if the level of cropping shown in the second was necessary for that image to "tell its story" it would be useless. It could be cleaned up and improved but it would still be the story of a sow's ear and making a silk purse. The third photo is about the same level of crop but captured at ISO 125 where detail is still well preserved. You can get away with suboptimal placement with great lighting but that is rare in most high school sports environments.
While you are deciding what or whether you need to upgrade, try choosing an optimal location for SOME of the action at an upcoming event. You won't get the overall coverage but it will give you a very good idea of what your equipment can accomplish when you are optimizing the capture in a suboptimal environment.
Rodger
