Saying past is past is like saying that someone who killed someone 10 years ago and wasnt caught should just be living on like normal.
Ofc it depends on how bad it was and I would just disregard stupid shit a lot of teenagers do sometimes which is not severe. Also things people did under 11/12 because most of them dont fully understand yet.
But if you bullied someone severely for them to develop major problems during the bullying and years after, maybe even considering suicide or wishing to transfer? All while you where old enough to know way better? Then I dont even care if it was 25 years ago, you have to pay for that shit.
Someone who tortures someone to the point where they develop mental problems and might even kill themselves doesnt deserve to live a happy bubbly life. Why do you all care for the career of such people? They are trash. Most people like that dont actually change, they just learn to be more discreet. And even the few who do, they are still trash. Good that they changed, but at some point of their life they seriously scared another person for years to come, killing them slowly every day. What kind of sane person would do that? And why would such a person actually deserve forgiveness if they didnt go out of their way in some way to earn it?