I think this is to black and white.
There are many reasons they didn’t apologize.
1. they were not aware of how much they hurt a certain person, so they didn’t apologize.
2. Many trainees barely go to school after starting the training, so they probably just didn’t had the chance to meet the person again to apologize.
3. Since they were absent from school they probably forgot the victim since they had other things to focus on.
4. They didn’t apologize because they might be more to the story then reported. You know there are often two sides of a story.
Also people can change, there is not such thing as bad person and good person, there are people who do more mistakes then others. Everyone is capable of changing we all did things we regret now being older.
But yeah you can’t tell if a person you don’t know personally really changed or not so you can’t 100% call it a fact that they have changed or not, it’s up to you to decide what you want to believe.