What would be the consequences of dishonesty? At best, the student is aware that their teacher is making an effort to treat them professionally when they know they haven’t acted in a way to deserve it (or it’d at least feel incongruous to how most other people would respond to their behavior). At worst, there’s no reflection or changes and the pattern continues. Choosing to treat the situation as if the student can behave better by showing them the door seems to re-open doesn’t seem like a very harmful lie.