Stupidity is not lack of knowledge. Lack of knowledge is lack of knowledge. Stupid is stupid. A smart person can be lacked of knowledge because he is simply lazy. Whereas a stupid person, takes a long time to, or maybe never grasp abstract scientific theories no matter how much he reads.

I'm sure you have come across people who don't study much till the last minute and still are able to do well if not better than you. Now that is a smart person, being able to understand and apply concepts in a short time.