Feeling like you don’t belong in the advanced class usually means you got there before your confidence did.

Selection happens on evidence and confidence arrives later, sometimes much later. Somebody looked at your work and decided you could handle the harder version, and your sense of yourself has not caught up with that decision yet. The gap feels like fraud and is actually just lag. Everybody in that room is quietly running some version of the same doubt.

Behave as though the decision was correct for a fortnight, because it probably was. Ask questions out loud, hand work in, sit near the front. Confidence follows evidence, and the evidence only accumulates if you stay in the room.