They saw the sign

I came outside for recess duty to this scene: in lining up for transitioning from the cafeteria to recess, Daphne had been spinning (or something) and smotched Ngan right in the face.  Ngan was sobbing and Daphne was giving totally guilty face.  I sent them to the office to get an ice pack and thought nothing of it.

15 minutes later, another teacher comes up to give me Part II of the story: she'd come out to recess a little late and had found Daphne and Ngan standing by the door that led out to the playground with unhappy faces.

"What's going on, girls?" she asked.  "Are you coming or going?"

Daphne replied, "We're trying to get back to recess, but" (pointing) "that sign says that the door has to stay closed and locked!"

Which is, in fact, exactly what the sign says.  Good for them.