'Dicipuli vestri miseri sunt' is actually more correct than the current 'correct' answer
Something can't be more correct. Both are correct and common in Latin.
With the verb "to be", I learned here it's common to have it in the middle of the sentence, or even at the beginning.
And even if it wasn't common, it wouldn't make it wrong, in Latin.
Why is "discipulae tuae sunt miseri" wrong?
"Discipuli vestri miseri sunt" is also accepted. But can this mean "they are your unhappy students"?
what about maestus?
Hence libros multos non legit.