Because Nick physically attacked her, Caitlin has been granted a restraining order against her boyfriend by the court. Under the terms of the order, Nick must not contact Caitlin in any way. As Judge Lehman tells him, if he talks to Caitlin at school or so much as looks at her funny in the hallway, he will go to jail.
The terms of this restraining order are more difficult to enforce than most for the simple reason that Nick and Caitlin still go to the same school, which makes it difficult to ensure that no contact takes place.
Responsibility for getting round these difficulties lies with the school authorities. They must make sure that Nick's presence at school doesn't violate the terms of the restraining order. They do this primarily by rearranging Caitlin's schedule so that she doesn't have any lessons with Nick. This also ensures that there's no chance for Nick and Caitlin to pass each other in the hallway, which might make Caitlin uncomfortable.
Nick's not very happy about all of this. He claims that the rearrangement of Caitlin's schedule so that he cannot see her makes her seem almost like a figment of his imagination. But then Nick, who's the abuser, is not really in a position to complain. He hurt Caitlin and it's only fair that he has to live with the consequences of his actions.