On the day of the final exams.
The first exam was Charms. Professor Flitwick stood guard in the classroom as students went in one by one and came back out. Only when Lynn entered was he told what the exam would be.
Before Professor Flitwick lay a pile of shattered glass fragments. He said to Lynn,
"Use the Repairing Charm to fix this cup. I'm looking forward to your performance, Belloc."
Lynn nodded and drew his wand. An exam like this did not make him nervous at all. He had long since mastered the Repairing Charm, an incredibly useful spell in daily life, to the point where he could not possibly be more proficient with it.
"Reparo."
He waved his wand at the glass fragments.
The fragments immediately rose from the table like soldiers receiving a general's orders, returning on their own to the places they had occupied before being shattered, ultimately forming a complete cup.
Professor Flitwick looked at Lynn's work with satisfaction and praised him.
"Perfect. An excellent Repairing Charm. I'll give you the highest mark, Belloc."
"Thank you, Professor." After bowing in thanks, Lynn left the classroom.
The Potions exam afterward was even less of a problem. Not only was Snape the head of Lynn's own house, but the two of them had worked together seamlessly to rack up points in Potions class. Just the fact that Lynn had helped tend Snape's potion ingredients ever since Raphael's accident was enough for Snape to put a huge O on his report card. (The detention room was Snape's office.)
Then there was History of Magic. Professor Binns might not have been much of a teacher, but this sort of pure memorization exam could not have been easier for Lynn.
That afternoon, there were two exams overseen by Professor McGonagall.