A complete predicate must start with a verb. 'The first day of the semester' is a complete subject. It is WHAT the sentence would be about. "With the new books and schedules in hand" is a prepositional phrase, which simply adds information to a sentence. "Because of the slamming of the lockers and the shouts of the students" is an introductory clause. "Could not be heard above the voices in the hallway" is the only complete predicate.
