Subtlety really isn't something Sherlock is trying for at this point. It doesn't matter. Any hint of it is more jest than anything, or a simple refusal to explain what he doesn't have to explain.

"Mm, exactly. Brilliant way to top off your last year, I'd think." His smile is still mischievous, wicked.

Subtle he might not be at the moment, but a talented mimic he is, enough so that the sudden change in the timbre of his voice and his accent might be a bit startling. Of a sudden he's less King's and all London, normal posh intonation entirely vanished.

"Show you how to sneak into the kitchens if you promise not to turn me in, copper," he says, and lets the character drop, wholly himself again in speech, posture, and expression.

"In fact, I've heard that there are at least two very accessible methods for sneaking into Hogsmeade, though I've never bothered to find them." Sherlock frankly can't imagine why he'd want to. Even when school is boring, getting away from it via that method is a mess he frankly doesn't want to entangle himself in. A good, clean expulsion would be favourable, though now it's his last year there's hardly any point in that either.