APPARENTLY, I LACK COMMON SENSE

A student in my class wrote "should" instead of "should not" on a test. I took a point off because it was a rather poorly written answer. He came up to me after class to argue the point. He said, "Anyone with common sense would know what I meant!"

Oh yeah?

Well, anyone with common sense wouldn't confuse two expressions that are as different as "yes" and "no."