Sorry, Newana, but this "...keep moodle from assigning partial credit to select all that apply questions. "..... is difficult to interpret.
You mean you have a multiple choice question and one option is "All the above" which is correct but if the candidate selects one other which is incorrect, they still get a partial grade?
Check the questions themselves in the Quiz editor, make sure that marks are only provided for the correct answer and the others receive no marks for any other response. That is the usual problem anyway.