"Tutup buku kalian!"

Translation: Close your book!

[Rick392366]

Close your books = not accepted.

I think it should be accepted as well.
Especially since "kalian" (plural you) is being used in the sentence.
It's reasonable to assume that we're talking about more than one book.

[atomic.bazza]

I agree, unless somehow a group of people are sharing a book but that seems unlikely

[Rick392366]

It's accepted now.

[mjzeekdaniels]

I was thinking exactly the same.

[Angela927992]

Shut your books should also be accepted

[sapere__aude]

Says sering perlu ini di kelas

[LukasOster1]

Why is it nit necessary to use the men- prefix as "menutup" to make it a verb?

[Rick392366]

When a verb is used in an imperative sentence, the 'me-' prefix is dropped.

[Kauakolo]

buku kalian = yʻallʻs books

[GordonDrum1]

Buku kalian is plural. Book changes to books but "y'all's" does not exist except in US southern slang. Perhaps you were having a joke.