As general info, I will say that drug testing in the military (regardless of branch) is relentless.
This may have changed but common test times at a SA in my day included the morning after a three-day WE and the morning after the school returned from leave -- sometimes that night. In the USN, it was common to show up at work and see a sign saying that everyone whose SSN ends in (pick two numbers) needed to report for drug testing. You were escorted to the testing area and had to stay there until you could produce a sample (plenty of water was provided!). Again, common times were right after WEs and vacations -- although any day of the week, any week of the year was fair game. If there was a workplace accident, everyone got tested.
If you do drugs, it's only a matter of time until you get caught. And, in today's military, you can consider it your ticket out -- with either an OTH or Dishonorable discharge. Not a career-enhancing move.
A single "experiment" as a high-schooler MAY not be fatal (depends on the school, circumstances, etc.). However, a single use once in the military -- including a SA or ROTC -- is almost certainly fatal to your military career. Those who have tried it in h.s. need to think seriously about the circumstances that led them to use drugs and figure out how they will deal differently with a similar situation in the future.