I think the latter depends on how the parents conduct themselves during the divorce.I'll be keeping an eye on the year 5's girls little brother next year, as a family breakup is never easy. Thankfully we have a social worker in school.
She's going to a different school, so I'll get in touch with one of the teachers/social workers there to make sure she's ok.
I think many people underestimate the effects of divorce and breakups has on children. They don't suddenly turn violent for no reason.