When you are learning at school, there are tests. The people who test you already know the stuff you are being tested on. If you are precocious, perhaps you will say something that the teacher hasn't thought of. Now that there is Google, Wikipedia and more than three books on each subject in the library, there may be more chance to catch teachers out if you are a nasty little critter.
As you climb up towards the end of school, learning starts to venture into interesting territory that isn't just learning the way things work. Even in the early years of university you are still covering territory that has been covered before. When you have a break through thought, it has still likely been covered before. You may think you are smart, you may be that nasty critter - with long hair and a beer. But as Will Hunting says, 'Don't do that'.
For the most part you are still surrounded by people studying things similar to you. You likely still have a professor who knows more than you. As you start to venture into new territory, the tables start to turn. The people who are testing you, know less than you. When you are at the very edge, the people who are testing you may not even have the language available to know whether you are talking rubbish or not. If you are an academic, there may just be a small group of people who know what you are on about.
Our ability to communicate our ideas becomes as, if not more, important than the ideas. It doesn't really matter what you know if you can't get it across to people, or work with people to get stuff done. To get stuff done, you also start working with people who have gone to different edges. They will have read different things, had different conversations, been in different places. Their whole way of thinking may be different, but they will still be testing you.
When artificial intelligence comes along, it is going to pull the rug out from many 'smart' people. If Elon Musk is right that we can completely replace fossil fuels with free sunlight, we are in for a big adjustment. Energy companies base a large part of their value on proven reserves. This is basically the stuff they know they already have that they can sell. If those suddenly become worthless. Rug. Pulled. The stuff you know is your proven reserves. That is why it is dangerous to base your identity on your job, or your worth on what you know. If artificial intelligence became available tomorrow, the value add people bring becomes creativity, empathy and the ability to communicate. Not what you know.