At what BAC level can people tell that you're drunk?

I'm going to drink 11 cans of 2.25% cider tomorrow during class over the span of 2 hours. Now, I won't get too drunk from this, max about 0.1 BAC.

Now I'm wondering how high of a chance is it that the teachers will know I'm drunk? At what BAC level can you easily tell that someone is drunk?