Just a thought, and maybe this isn't the best way to do it, but I would add an additional field per question. It would be a formula field numeric. You could hide it from the students.
Then in your formula, you could use either a CASE or IF statement, you identify the correct answer, filling in the field with a 1 for correct or 0 for incorrect.
Then you have an additional field or a summary, that totals all the 1's, giving you an overall total.
Then in an additional field you score it out, i.e. 15/20
Hopefully that helps.
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Andrew Fry
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