Anastasia was worried that the two siblings would be seen as henchmen, it could happen because the real culprit had now become a victim of Zach's malignancy.
It could be that the delinquent man made false statements and cornered Zach and Leonard for punishment. Only Anastasia, Tiana and Instructor Nell know the truth about this delinquent man. She must immediately provide the principal and Instructor Logan with this valid information.
Without waiting for a second, Anastasia invited her friends to get ready and go to the academy. Even though her efforts would not be able to justify Leonard and Zach's actions, at least she wanted to lighten the punishment that was going to be given.
Since the Academy was always open to students, Anastasia was able to reach the principal's office without a hitch. It's just that she hasn't confirmed whether him was in the room or not.