David takes advantage of his new tech to get revenge on his bully. Doing it at school gets him expelled, of course, but that's not the problem. His Sandevistan augment is visible on camera, and his bully is the son of Mr. Arasaka, head honcho of a major corp.
He recognizes the Sandevistan on video and notices that, unlike the previous owner, David is not suffering from cyberpsychosis.
Perhaps it would be useful to bring him in as a tester.
On the Subway, David catches Lucy stealing chips from the passengers.