You can't pass the knowledge of the teacher. What's the "smartest" possible AI?

Found in proverbial truisms since for thousands of years, it is a proven fact you cannot exceed the knowledge of the one teaching you (you can get another teacher - but that is a different aspect)

Any given teacher can only impart what [s]he knows (or thinks)

So what does the 'smartest' or 'most-knowledgeable' AI actually look like?