Haha if your username is true, then we are probably in similar situations. Just started university at 30 to change careers. I'm definitely the oldest student in most of my classes(which is such a new feeling for me), and I might even be older than one or two of the teachers I've had. I'm obviously not old, but in comparison its hard to relate to a lot of my classmates on an emotional level. I see quite a bit of this stuff among other students, not necessarily directed at me, or maybe I don't care enough to see it.

Just sat there quietly and there are two girls who usually sit in front of me that involve me in the group discussions but I didn't want to bother them because I feel like they kind of talk to me out of pity.

If they're engaging you, engage them if you'd like. Saying they're doing it out of pity might be you overthinking it. Realistically if they were doing that, they probably have more empathy than all of my own classmates combined and are worth spending time around anyway.

I figure a lot of kids are still working out their own insecurities too and probably have a lot of the high school ingroup/outgroup "lets find someone to put down or ostracize" mentality. It's completely obnoxious and disrespectful. What I find helpful is going out of my way to join a group when we're breaking up to discuss a subject or work on a lab. Then just stagger conversation between the task you're doing and surface level chat. I find it makes people way more pliable.

Sometimes there's nothing you can do and they're just gonna be a little shit no matter what. Personally I consider if its worth it to just be upfront. Am I gonna be working with this person with a lot? Usually a quick "Why do you [thing they do that is frustrating]" is enough to embarrass them and maybe reframe how they approach you.