Is the transcript sent by the GC via CommonApp considered official?
I heard that the colleges check back with the school after acceptance. So, is the transcript reverified even if it is sent by the GC? (i.e. the transcripts from grade 9,10,11)
Can someone give me some idea as to what do the colleges discuss with the school when they call/email?
Yes, the transcript sent by the GC is considered official. Pretty much all colleges will expect a final transcript at the end of the year. It is not typical for colleges to contact a school about an individual applicant unless there is a question or a problem.
To second collegemom, the transcript uploaded on CommonApp is considered official, and colleges will expect a final transcript at the end of the year.
I wanted to add that many colleges will attempt to verify a random set of credentials as a fraud prevention measure. If it is ever found out that you cheated on your application, even years after you graduated, you may face penalties such as your degree being rescinded or having to repay scholarship/financial aid money. (This occasionally makes the news when someone worked their way up into an influential position, such as CEO, and faces increased scrutiny about their past…)