In middle and high school, I usually felt at least a few years behind everyone else, even though I was usually never the youngest in my grade. I could tell that people thought I was really immature too, but I didn't know how to fix it. As I got older I hoped that I would catch up to where my peers were, but the opposite happened. I retained the maturity of my middle school self well into my senior year, despite being more intelligent academically than most if not all of my peers, so the disconnect was even more extreme. The fact that people thought I was smart made them expect more of me, and I often had people telling me I should be able to do this or that because "you're not stupid".
Honestly, I still don't feel like I've matured much socially. I tend to avoid social interaction of any kind now, so I think that just makes me look like I'm a loner, which is better than people thinking I'm extremely immature at least.
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"It has long been an axiom of mine that the little things are infinitely the most important."
- Sherlock Holmes