You are wrong.<quoted text>
Thanks, Mrs Teacher.
May I interject?
A double is a writing form using two negatives to express a positive, like the examples you gave.
However, "That does not mean that you are not ignorant" is also a double negative. You used two "nots" when you shouldn't have. The correct sentence would be "That means you are ignorant".
To say "that does not mean you are not ignorant is grammatically correct".
YOU are welcome.