I agree with Tony. Personally, I'd say that nearly all karate schools teach, at some time, the things which "are against the rules," even if they are a sport-tournament training school only. You have to show that stuff so the student can understand why it is against the rules.... because they are so dangerous.
I teach people "in here vs. out there." In here, we're at the dojo with our friends and training partners, and we don't want to hurt them because first, we like them, and second, we won't have anyone to train with next time.
But, out there, in the world, the simple things you do to keep things safe, you can simply elect not to do and render a technique very bad indeed.
Simple example is judo one-shoulder throw, ippon seoinage. In dojo, strike comes, evade, enter throw, turn hips hold up on uke's arm, they fall safely on the mat, grin and get back up.
In parking lot attacked by bad person, strike comes, evade, enter throw, pop hips to send opponent up and over, back out while opponent in the air and let go, let them see how they do against gravity, they groan and generally do not get up.