She doesn't tell him she's figured it out. One, she's pretty sure Batman would kill her, bury the body somewhere, and maybe replace her with a robot to keep her mom from trying to murder him in return. Two, it was actually pretty hard and she figures he might as well keep his sense of victory because it's admittedly well earned. She only got it because someone shoved past him in the hallway and in the moment between falling and standing he didn't fall.
Still, the day Dick Grayson wins a mathlete competition (apparently second year in a row) Artemis cannot keep a straight face in the cave. Her second burst of laughter for no reason makes Superboy get up and stalk from the room, but he does that a lot anyways.
Dick corners her in a hallway after he calculates some distances on the map and she cracks up for the fourth time that day.
"You know," he says, irritated, and she grins. She feels a tiny bit guilty but not that much. "I told him it was stupid sticking you in the same school as me," Dick (Robin, it's always got to be Robin when they're in the field or the cave) says indignantly. "I told him you would figure it out."
"How long did it take you to recognize me, ten seconds?" Artemis scoffs. "You've still got me beat."
"Two days," Robin admits, and she grins.
"It was when you saw my rock-hard abs in gym class, wasn't it?" she says, and he rolls his eyes.
"You're ridiculous," he informs her.
"And you're a mathlete champion," she says. "I'm sorry, who's ridiculous again?"
"I'm going to murder Batman for this, you know," he says, and she slings an arm around his shoulder, dismissing the sinking feeling in her gut at how small he is.
"Yeah, let me know how that goes," she says.