So here's the thing, the one factor of this entire equation is that you can only control is yourself. You're not going to change all of these people from treating you the way they do. The only thing you can control is your reaction and your attitude going forward.

I think /u/bonzo14 said it perfectly here:

What I'm saying is don't take it personally. They do it to sooooooo many other people too.

More likely than not these people don't sit around and try to figure out how to make you feel awkward or uncomfortable. It's just stupid shit that kids do to a lot of people. It's immature and annoying but as long as you're safe and they're not straight up bullying you I think you'd best adjust to the situation by changing how you view this. It's not an easy thing to change how you feel when it happens but it's the one aspect you have control over.

But it's not even people who are at my age who doing it, even a teacher talks down to me like I'm a child.

This in particular strikes me as really odd. I'm not saying teachers aren't capable of being total dicks, but if you're feeling like everyone around you and authority figures are treating you a certain way, I'd say there's a chance that your perception of the events might be skewed. It might not be entirely accurate to what the people originally intended to express.

Calling you out and saying "Omg! So-and-so is actually talking!" isn't just a school thing. I'm almost 30 and I'm still getting comments like that. People don't usually say it to be hurtful. They're just talking without thinking. I also can see how in school they may say it to tease you a bit, but it doesn't mean it's always malicious.

It's never particularly bothered me when people call me out for being quite except the frequency in which it happens. My first thought is always a sarcastic, "Yep. Never heard that one before." As I've gotten older I've recognized it more as a way for people to pull you into conversations, though. It's like an opening line for them to mean, "It's okay for you to talk! We want to know what you think, too."