Nope, wasn't shown this at any of the schools I went to, be it dress code or not. Even with dress code it doesn't prevent the whole waistband pistol holding, or the shoulder-strap if you have a jacket on. And if having your shirt tucked in is part of the code to prevent that, theres always the good old boot/ankle strap gun. As for the video loadout, apart from being overly dramatic and ridiculous, I'd love to see how well they would be able to walk, jog, run, and even just sit down without someone going 'hrmmm?'. Hell, you'd get more odd looks than I did when I was walking around the halls with my longbow and quiver slung on my back when I was with the archery group.
Besides, even with a dresscode, how does that prevent someone from, oh I don't know, using their backpack to hold their guns?