I took an exam and the test included this exercise Rewrite the sentence:
Don't stop us doing what we want!
-> Let.................................
At first I thought it was "Let us do what we want", but when my teacher corrected, she told us that the answer was "Let we do what we want". Still, she said that the first one was ok. I have never heard "Let we do what we want" so which one should I choose?
Your teacher is wrong. "Let us do what we want" is correct; "let we do what we want" is never right in standard English. Also note: in any kind of formal writing, using more than one question mark is an error.
From a question on English Language & Usage Stackexchange:
Us is accusative since it is the direct object of let. Disambiguation might help:
Allow us to go.
The convention is to delete the to from the verb after let; otherwise it is the same as allow:
Allow them to come here turns into Let them come here.
"Let we..." is not correct. It's not correct now and it never has been, at least in Standard English. You need to use the objective case here (i.e. "us").
I'm a native speaker of American English, but you can verify this yourself by searching COCA for . let we (note that the period is used so that it only finds "let we" at the start of a sentence; you will need a free account to do this search). Out of the multitude of words in the corpus, there are only two matches, both from the same work, which are examples of intentionally broken English.
