It’s not just indifference, schools often create conditions that encourage bullying and perpetrate it themselves. Ranging from little things like letting kids pick teams and groups, to big things like dress up days - which I’m sure are great fun for kids who have creative parents that make them fabulous costumes to show off, but for the kids who don’t have any support and are left trying to cobble together something on their own with no resources those sorts of things are a nightmare. It would be so simple to improve these things with a bit of thought. Change the way teams are selected. Don’t allow any assignments or activities that rely on parental involvement or having any particular type of family. If schools want to do dress up days they can do it as a group activity, costumes can be a shared resource not platform for kids to see who has the best parents.