i don't think it's that bad but generally u get bullied if you "stand out" or is "different" from everyone else. not really much different from other highskool where kids get bullied for being different: Homo, Nerd, Emo, race, etc. also manga usually exaggerate things
Kids are dumb and will find any reason to bully someone. I have crazy curly hair and was made fun of for it all the time. I love my hair though, so their attempts failed.
Do people get bullied for having natural curl in Japan? thats just too sad, I love curls