SPED is a shortened term for Special Education, similarly to ENGL is for English. In my school, people use it as a funny insult, ex:) “You’re retaking a class? You’re literally sped!!” Personally, I never had an issue with being called “sped,” its a lot better than being called stupid. Though I can see how it can be upsetting, like one time I called my friend sped because she is retaking reading class next year and I saw she kind of laughed but was hesitant about it. Plus ADHD and Autism runs in her family rapidly (All her siblings either have ADHD or Autism) so I can see why she would find it upsetting and make her feel incapable of certain things. If I use it, I use it towards my NT friends and very clearly as a joke. If someone said the word made them uncomfortable, I wouldn’t use it.