PAX, No human instructor is going to be able to physically stop someone from muzzling another shooter without being hands-on the weapon all the time. Sometimes you need to trust the students.
BreacherUp, I've worked the line enough times to know that it's not physically possible to be three places at once.
But I've also observed enough well-run firearms classes to know that there are certain very predictable moments -- and certain very predictable
students -- where the instructor can often sidestep a burgeoning safety issue and prevent it from growing.
One such moment is the very first time a student fires a shot. A
huge number of new shooters WILL turn around after that first shot is fired, no matter how much you warn them not to do it. A good instructor knows this and plans for it. (Load one round at first. Run two or even three relays so you have enough assistants to put one in between every two students. Whatever! Just
plan for it.)
Another such predictable moment is the very first time a new shooter learns how to work a slide. Muzzle control will be nearly nonexistent and trigger fingers become very wayward. It's predictable and therefore worth planning for.
Also, some students give off very clear watch-me vibes. In those cases, you park an assistant right at the guy's shoulder, and give him no opportunity to create a serious danger until you are convinced he is ready to be trusted for at least two whole blinks at a time --
ESPECIALLY during those predictable times of heightened danger. From the OP's description of his range neighbor, it sure sounded like that student was giving off the watch-me vibes, which was why I asked about instructor/student ratios. If one instructor was trying to work with 6 or more students, he did very well to pounce on the violation at the very moment it occurred. But if he had better ratios than that, the instructor did a bad thing by not perching at watch-me guy's shoulder until the most dangerous moment (of first slide manipulation) was safely past.
pax