Childrens book - School (?) which has a machine that steals children's creativity/ individuality to make them well behaved and stores them (creativity) in jars

[Maria]

There were these two parents and they were both scientists/doctors and they had a young girl who got kidnapped and talen to this school too. Not as a student but the main antagonist wanted to keep her as a daughter for herself? The dad was known for being able to crunch through an onion as if it were an apple. Specifically remember that from it

The school had a sort of machine which would need a child to sit in a chair and have these things attached to their head and it would take away their ‘disobedience’ and it would be stored in jars which were labelled. And you couldnt just break the jar to give it back it had to reverse through the machine. Uhh i also remember there being a car somewhere? Idk

I read this when i was about 10

[Pony]

I read a book called A Tangle of Knots, which isn't the book you're looking for, but it had people's Talents getting stolen and stored in jars.
There's a sequel to it that I haven't read yet called A Clatter of Jars that involves children going to a summer camp and still deals with conceptual things being kept in jars like that. Since I haven't read it yet, I don't know if anything else fits your description, but I thought I'd take a shot since your post made me think of it.

[Kris]

Google Books preview of A Clatter of Jars by Lisa Graff - Pony's suggestion:

- https://www.google.com/books/edition/...

[Bridget]

Wakestone Hall by Judith Rosell has a machine which sounds similar.

[JB]

The Girl Who Could Fly by Victoria Forester has some elements kind of like this too…