If you did something fucked up and heinous in school you don't pull the "I don't recall." At the very least you admit it. If it was really fucked up you apologize.
I refuse to completely own up to something I genuinely don't remember. That's a real can of worms to open up.
I won't outright deny it, but I'm not admitting it either.
I gave an example in that thread.
If it happened (and my friends swear up and down that it did), I'd be sorry that it happened, but I couldn't really make it sound genuine.