I don't think posting that you got into a good school is concieted- it is sharing with friends and family a life changing event.
I think posting that you just got your hair cut, are dusting, are tired etc... is concieted for assuming people really care that much about the minor details of your daily life.
Also " I got into my favorite schools" happy posts, are much less aggitating than the "I didn't get in anywhere" sad-story-cheer-me-up posts (not saying I'm not guilty from time to time, I just know I'm being obnoxious when I do it).