Replying to Physical, and Im a tad worried

I've gone through a couple prior threads and concluded that they won't do a drug/alcohol test unless your parents ask them to, but Im not completely sure of this and wouldnt mind some new opinions.

I've heard that its easy for them to notice when screening it but they can't tell your parents, I've also heard if your under 16 they can, and Im 15. If the physical is for a school sport, would they report that? Has anyone got fucked over from a physical, or confronted by their doctor about health issues from drugs and alcohol, because that would be so incredibly akward I'd probably punch myself in the face. Plus my mom and my doctor (woman) are kind of friendly.

Confirmations? Stories?