Bullying is inherent in institutional life – never believe the contrary. There are many causes but good schools try hard to eradicate it and will probably have a formal code. Poor schools pretend it does not exist. You may find Heads’ attitudes illuminating.
Remember your child may be either the bully or the one who is bullied. If you think your child is being bullied, tell the Head or housemaster/mistress. The problem may not be soluble immediately but a good Head will find out what’s going on and can advise you and your child on how to deal with it. Approaching other pupils or parents directly is strongly discouraged and can cause further distress. If you get no help, or if your child continues to be unhappy at school, investigate further; you might have chosen the wrong school.