Dear readers,
in my English test paper I wrote the following sentence that was marked to be a failure. Knowing my English teacher for quite some time now, I am not sure whether there really is a mistake or if she just simply doesn't recognize the construction. Here we go:
It is very important that Scottish finance system not be ruled by the Bank of England.
Thanks for your wise answers!
Thorsten T. Rufus
Dear readers, in my English test paper I wrote the following sentence that was marked to be a failure.

I think you mean "mistake".
Knowing my English teacher for quite some time now, I am not sure whether there really is a mistake or ... construction. Here we go: It is very important that Scottish finance system not be ruled by the Bank of England.

This construction is correct (a subjunctive (Konjunktiv I in German) although quite formal in british English (I believe it's more common in American English). More common in British English would be "... should not be ..."
I suspect your teacher might not have recpognised the structure as it would usually only be dealt with at quite advanced level.

Einde O'Callaghan
(English teacher working in Germany)
It is very important that (the) Scottish finance system not be ruled by the Bank of England.

As amended.
Owain
Students: We have free audio pronunciation exercises.
Owain schrieb:
It is very important that (the) Scottish finance system not be ruled by the Bank of England.

As amended.

Thorsten,
Which part of the sentence did your teacher mark as being incorrect?

Regards, Einde O'Callaghan
Dear readers, in my English test paper I wrote the following sentence that was marked to be a failure. Knowing ... that Scottish finance system not be ruled by the Bank of England. Thanks for your wise answers! Thorsten T. Rufus

As Owain noted, the error is you need 'the Scottish ...'.

Did you not ask your teacher what your exact error was?

Did she not explain why you were wrong?
Which part of the sentence did your teacher mark as being incorrect?

She underlined the following parts:
It is very important that Scottish finance system not be ruled by ^^
She counts this "mistake" as gr (=grammar) one, as noted on the left side.
I haven't had time yet to speak to her. It won't have any influence on my mark anyway, it's just a question of who is right.

Thorsten T.
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One could even omit "that Scottish" and replace it with "the Scottish."
Which part of the sentence did your teacher mark as being incorrect?

Thorsten T. Rufus wrote back:
She underlined the following parts: It is very important that Scottish finance system not be ruled by ... her. It won't have any influence on my mark anyway, it's just a question of who is right. Thorsten T.

Thorsten, I think that your marks might have been moved around, as I discovered when I replied to this post that opening your response in a Google Groups reply box moves your makeshift underlining around. I suspect, however, that this is not the case.
If your teacher underlined the section marked above, you're wrong and she's right. If she underlined the subjunctive part (...not be ruled by...) then you're right and she's wrong. It is hard to believe that anyone who teaches the English language to foreigners would not be exposed to the subjunctive somewhere in their preparation to do this job.
Precisely why she's right has to do with one of the hard-and-fast rules of English grammar: except in certain very common collocations/word groups (go home, in school, in bed, at universty, etc.), singular countable nouns in English like "system" must be preceded by one of four different word types: a possessive pronoun (her, his, its, etc.), a possessive adjective (Mary's, John's, Thorsten's, etc.), an indicative/demonstrative pronoun (this, that), or an article (a, an, the, any).
I tend to call this the first Golden Rule of Determiners when I teach it.