At this point, can it harm my chances at other schools (decisions arrive within a week). I know it sounds paranoid, but I just want to make sure! Thank you!
I don’t think so! Just say “accepted to _____” (I’ve seen others do it)
@hungrihippo thanks!
Just mentioning where you got accepted on social media is fine. I’d think it’s not too wise to join one of those “_____Class of 2021” as that implies you may have already committed to that particular school.
@TiggerDad no I don’t believe it does. I have joined multiple FB groups (including one for Georgetown, where I was admitted EA) and continue to receive acceptances (I am in at GTown, Lewis & Clark, Middlebury, Barnard, W&M and Scripps). Those facebook groups are often used to gain more info about the school.
However, posting that you are committed to a school may hurt you.
@yonceonhismouth - The key words are… “I’d think it’s not too wise…” I mean, you only have a week to go to have all the dust settled. Sure, the odds of some admissions folks finding out about your “________ Class of 2021” is very unlikely, but why not wait just one more week to gloat? It’s good for your discipline.
@TiggerDad I think the difference we’re talking about is posting “_____ Class of 2021!” acknowledging your commitment versus joining the group.
the FB groups are full of students not quite sure yet, and are a way for the admissions offices to give prospies more information before they make a decision. I think college admissions officers would know that joining the FB group does not imply commitment.
@yonceonhismouth - Well, you do what makes you happy. 
no, it won’t harm you. I posted about all of my acceptances two years ago (the last four in separate pairs), and joined all the group chats/FB groups, but later announced my commitment to my current school saying “OFFICIALLY A MEMBER OF ______ CLASS OF 2019”. Honestly, FB groups and group chat apps are a great way to help you narrow it down. I got a great feel of who I’d be going to school with through peer interaction, and this made my choice MUCH easier.