Among the Impostors (Shadow Children #2) by Margaret Peterson Haddix

It was awful. All those eyes, all looking at him. It was straight out of Luke's worst nightmares. Panic rooted him to the spot, but every muscle in his body was screaming for him to run, to hide anywhere he could. For twelve years his entire life he'd had to hide. To be seen was death.

"Don't!" he wanted to scream. "Don't look at me! Don't report me! Please!" But the muscles that controlled his mouth were as frozen as the rest of him. The tiny part of his mind that wasn't flooded with panic knew that that was good -- now that he had a fake I.D., the last thing he should do was act like a boy who's had to hide. But to act normal, he needed to move, to obey the man at the front and sit down. And he couldn't make his body do that, either. - from Among the Impostors

Luke Garner is terrified.