I mean, have you really never met anyone who's one way around some people, and another way with others? We should all be so lucky! I've had co-workers who are total assholes to colleagues, but become simping ass-kissers in front of higher-ups. Or kids who are angels at home and absolute terrors at school. Or the other around: they're angels at school and terrors at home.
Darem was sweet, deferential, and dutiful for Kaira (and his parents' approval), and then he let himself loose for the first time at the academy when he didn't have any of that baggage on him. That's not at all different from kids who grow up in strict homes, then basically go hog-wild when they go off to college, and then later grow out of that wild phase.
I understand why they didn't want to put all the time (and money) into everyone's make up, but, story-wise, that was pretty inexcusable.