Andrew hurried into an empty classroom far from the scene of the incident, conjured paper and ink with Transfiguration, and jotted down a few notes on Peeves's strange behavior. Then he set them aside.
Controlling Transfiguration had troubled him for a long time. Professor McGonagall had told him that the subject was usually introduced in the second half of Third Year. Although he had mastered most of the theory, he would need to reach Second Year at the very least before tackling it.
Even with barely adequate magical development, mastering a field that demanded such precise control would take a great deal of practice.
It was on an entirely different level from the commonly used Scouring Charm. The Scouring Charm only required the caster to identify the main object; anything outside that category would be cleaned away. Partial Transfiguration, on the other hand, meant identifying one component of a mixture and casting a spell on that component alone.
As one reference book put it: master the Scouring Charm, and you could find work washing dishes in any restaurant. Master precise control of Transfiguration, and you could make a tidy sum processing herbs.
Of course, Andrew was still a long way from that level. Extracting potion essences with such precision was something covered only in Advanced Potion-Making.
The most basic application of that control in Transfiguration was transforming a living thing.
Not the simple kind of transformation that turned a beetle into a button, but one that accurately located the signs of life in a living creature and transformed it into another living creature.
The former was taught in Second-Year Transfiguration. The latter was something many Fourth-Year students could barely manage.
In short, if he demonstrated this to Professor McGonagall, he could undoubtedly skip the Second-Year exam and receive an Outstanding.