By/with

My sentence as usual:

-TS Eilot began the poem __ a German excerpt.

I used by; my non-native teacher gave me zero marks and said only with is correct. But by sounds OK to me. Do you think I should have got the mark?

Could I say this?:

-Foreigners force their idea upon young people so those young people would grow up as Foreigners would like them to be.

1. It is talking about the present, and no hypothetical thing is made. I think would is wrong, and will should be used.

2. be is wrong and should be omitted, because be does not fit in with grow up.

Do you agree?

... began the poem with ...
You cannot use 'by', unless it is followed by a gerund, like giving.

In your second question, omit the 'would' prior to 'grow up'. You may substitute 'will'.
Either omit 'be' or replace it with 'become'.

Foreigners force their ideas upon young people so they (will) grow up as the foreigners would like (them to | them to become).

Excellent answer. Thank you.
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For the 'would' part, do you agree with me that because of so (=so that/in order that), we cannot use would, and so refers to a likely situation, which is not compatible with the hypotheticality conveyed by would?

In this case, the omission of 'would' is preferred because of the tense of the verb in the main clause.

You may use 'would' in a clause that is introduced with 'so', but only if the main clause verb allows that.

Excellent answer. Thank you.