I joined chess.com in November last year, but only really started playing after Christmas. I quickly got better than many of my friends who used to beat me easily. Now, after 4 months and ~850 rapid games, I've reached a 1700 rapid rating. Is this considered fast? (btw I'm a high school junior)
Compared to me, ur a god, I'm only 1540 on rapid 
Edit: I just saw that you've played 850 rapid games in the last 4 months. Wow! That's an incredible amount of effort that you've put in! And here I thought I was doing well with 150 rapid games in that timespan lol (though to be fair I also have almost 1000 blitz games since then.) I am very very impressed.
Thank you! Admittedly, probably 150 of those games were ones I played with my brother lol.
kudos!
I trust him and its amaizing. I also started in December but Im doing a little bit slower. If its fast 'impossible' progress it doesnt mean it will continue. We dont know, for example maybe I will never reach 1600 and this is my maximum. Try your best and good luck. :)
I started out in October, playing almost exclusively against bots. Before that, I hadn't played in 15 years. I knew how the pieces moved, except for en passant, pawn promotion, and I couldn't remember how to castle. In January, I joined this site to play humans. I'm hovering around 1150, and I'm actually quite proud of my progress. Discovering chess has been great for my mental health.
How are your simple high school class grades? The real life stuff. If you are good at chess but let other things fall, then it probably isn't worth it. The only people impressed by good chess players are other chess players.
Of course it's fast. I think this post is a brag. It would better if you bragged openly: "I just wanted to share my progress and how proud and excited I am to learn this game", etc.