I think this is tricky, but I think that there is definitely a line across which it isn't right to have an abused pupil see their abuser every day at school, and that for a child who crosses that line, it's potentially not safe for staff and other pupils either.
For example, in my DS2's class (primary), there's 3 kids with some issues - the school is handling it very well - working with the parents, having extra support for those children, having strategies around it all, the rest of the class is aware, and asked to be tolerant, but also supported in their boundaries around obviously not wanting to be hit by these kids. This is normal stuff. If there was a child who was victimising another, who was attempting to assault another (sexually or otherwise) intentionally, rather than as a result of not really thinking/heat of the moment, or if the heat of the moment child wasn't being supported to stop those incidents, then I think that crosses the line, and exclusion (but then helping the parents find a suitable alternative, not just abandoning them) must be the solution for all concerned.
I have a family member who went to a special school when at primary, then was in a high school with a special needs unit for secondary. I understand why it's done, but I think that it didn't do him much good - I think that some children it would have been great for, but as children have individual needs, they need individual solutions.