I know that when I played back in the stone ages that when I got to college the players on my team told me that they all had been on steroids for a couple of years and so were, in some cases, close to half of their teammates.
The way we stop it is that unlike the pro athletes who can afford to keep taking stuff that can not be tested for, most high school athletes are taking stuff that can be found. I say that you make all students in all extra curricular activities take mandatory drug tests and at any time they are found positive they lose the ability to compete within that season.
For example, let us say that Johnny Smith takes a cycle of steroids and when the season starts up he is tested and fails. Johnny stays ineligible until basketball season at least and he is required to be tested periodically during the remainder of the school year. I say we do it for all drugs not just steroids.
But of course this will cost millions of dollars and no school district can afford to do it to the extent that it needs to be done to actually nip it in the bud.