The fourth-year curriculum had the shape he had expected. Arithmancy moved into vector theory, which he had long past worked through and found more interesting in practice than in abstraction — the way the numbers described relationships rather than quantities, the specific grammar of a system that was trying to say something about how magic moved. He made notes in the margins of the theory text not to record what the book said but to argue with it, which Babbling had told him in third year was the correct use of a margin.
Ancient Runes had a gap he had identified in August: the transitional period between classical and medieval runic systems, a hundred years of inscription work that the standard curriculum treated as a bridge passage rather than a subject in its own right. He had ordered three texts from Flourish and Blotts and worked through two of them before term started. The third arrived in the second week, carried by a very tired owl that had apparently taken the direct route from Edinburgh at full speed.
Babbling, when he mentioned the gap in her Tuesday session, looked at him over her workbook with the expression she had when he had found something she considered worth finding.
'The Northumbrian transitional corpus,' she said.
'The inscriptions don't fit the standard grammatical model,' he said. 'They're using structures from both systems simultaneously — not as a bridge between them but as deliberate synthesis. Someone was doing something with the combination.'
'Yes,' she said. 'This is not covered until sixth year because the standard curriculum doesn't have sufficient grammatical foundation in place earlier.' She looked at him. 'You have the foundation.'
'I know,' he said. 'I'd like to work through it.'
She produced a folder from the cabinet behind her desk that had the quality of something prepared and waiting. 'I thought you might,' she said, and handed it to him.
He looked at the contents — her own notes on the transitional corpus, assembled with the specific careful architecture of someone who had been thinking about a problem for years and had developed opinions. 'Thank you,' he said.
'Don't thank me,' she said. 'Write me a proper analysis by the end of October. I want to know what you think they were doing.'
Care of Magical Creatures had moved into the section of the fourth-year curriculum covering creatures with complex magical properties — the category that included Thestrals, which Hagrid introduced in the third week with the specific careful manner of a teacher who understood that the visible and invisible populations of a class were not always the same size. He taught the theory of thestral biology to the whole class and the practical observation to the students who could see them, which on this particular occasion was four, one of whom was Ron.
He said nothing about this. He observed the Thestrals from the correct distance with the attention he gave things that were genuinely interesting and took notes on the wing structure, which was more complex than the standard texts described.
Transfiguration had reached the stage of fourth-year work that he found most demanding in the specific way of things that required not power but precision — the partial transformation, the controlled maintenance of a halfway state, which asked for a quality of sustained attention different from completion. McGonagall ran these sessions with the methodical rigors of someone who had been teaching the subject since before most of her students' parents were born and had long since identified the exact point where technique failed and intention had to carry it. He worked through the exercises correctly and received, at the end of the third session, her specific nod — not praise, but the acknowledgment she reserved for work that had met the standard she had set rather than the standard she had expected.
Potions he handled with the care he had always given it — present, accurate, producing results that were correct without being conspicuous. Snape taught fourth-year Potions with the quality he brought to everything: the assumption of inadequacy, periodically revised for specific students, and the complete refusal to deliver information the student could find themselves. Ron had decided in second year that this was actually a reasonable pedagogical approach if the underlying knowledge base was sound, which for him it was. He found the sessions useful and did not perform finding them difficult.
The Defense curriculum under Crouch Junior remained the one he navigated most carefully — showing enough to demonstrate competence and not enough to demonstrate the gap between his competence and the curriculum's level, which widened every week.