"Maybe she didn't know it before," shrugs Seamus.

"But why do all the people who don't know they don't want to be teachers try out this one subject?"

"It's the only subject that's always open since no one lasts more than a year," he reasons.

"I guess. How long has this been going on?"

Shrugs all around.

...Okay. She makes a mental note to look it up later.

Next they have Transfiguration with the Ravenclaws.

Ooh. Are there any open seats next to Ravenclaw girls, she does not want to limit her socialization to her own House.

There are! There's a girl without a partner there.

She sits beside her. "Hi!"

"Hi!—you're Dorea Potter! I'm Mandy, nice to meet you."

(There's a tabby cat sitting on the Professor's table with strangely intelligent eyes, watching the students arrive.)

"Nice to meet you too!"

"How're you finding Hogwarts?"

"It's glorious."

She giggles.

The cat watches them intently.

Wait.

Didn't someone say the Transfiguration Professor turns into a cat?

And at 2:30 sharp the doors slam shut and the cat jumps from the table, turning into Professor McGonagall in a fluid motion that makes several students gasp in surprise.

"Transfiguration is some of the most complex and dangerous magic you will learn at Hogwarts," she says without preamble. "Anyone messing around in my class will leave and not come back. You have been warned."

Then she wordlessly waves her wand and changes her desk into a pig and back again.

Ooooooooooh.

She starts explaining a lot of complicated stuff on which they're supposed to take notes, and then she gives each of them a match and tasks them with trying to turn it into a needle.

She takes notes and then diligently attempts to needlefy a match.

It does not go.

She tries harder.

"Harder" may possibly not be the thing she should be trying, here.

She tries a different tack.

It is really difficult! McGonagall said something about having to twist your mind just right; it's not something that can be brute-forced, it needs to be finessed, you need to understand very well what you're changing to what and how.