Mark stopped, and stood up very, very straight. It was a learned response to an authority figure. He was not in motion, or about to initiate anything, but nevertheless he stopped. Completely. He did not blink. He did not draw breath. His heart, even, ceased to beat. It was truly a triumph of SHIELD psycho-conditioning. And at the loud pronouncement of 'GO!' Mark tensed and jumped half an inch in the air, autonomic functions resuming at natural pace. The obedience was immediate and absolute; Mark began to walk away from the school grounds at a brisk pace. Nothing superhuman, of course, but with the obvious speed of a retreating, chastised child.