Just leave the loner kids alone until they grow out of the awkward teenage years.
As someone who was bullied in school, I have a different take. Were I running a school, there would be cameras everywhere and I would come down like the FIST OF GOD on any bullies. Many bullied kids are physically incapable of fighting back. The bullies are nearly always bigger and older. They target certain kids because they’re cowards and want victory to be a sure thing. God help them if I was running a school.