Stop fidgeting. Idiots, you know, also think they are intelligent. I already explained to you that many different people think you are an idiot. This does NOT mean that you are unique. It means that you are stupid.
By the way, I don't consider myself particularly smart; I just don't think I'm stupid.
Let them think. The main thing is that those whose opinion is much more important to me than yours don't think so, for example.
Therefore, referring to your age is purely an explanation of your stupidity, and not an attempt to prove that you are stupid because you are young.
A 20-year-old girl asked me how old I was, and I answered her, and she said: "Wow, you are quite smart for your age"