If the students and parents were warned about this, which they probably were, then it’s too bad. Other people have a right to enjoy their graduation ceremony without it turning into a hooting and hollering contest.
I can almost guarantee they were warned about it. I've been to more than a few High School graduations in Cincinnati and that warning was given at every one of them. Hold all applause until the end, because these events are long enough with 500+ graduates.
It's like someone already posted, there are always people at these events who lack restraint and decorum, and when they act like children even after the warnings, other people do not get to hear their loved ones name being called.
That reasoning is given along with the warning, but some people just do not care.