Created households not showing up on high school?

I may have found a solution! I was having this same issue but then I had one sim I was playing meet a sim from another one of my household's in the same world and the next day I saw my other household sim at school and it said "student" under their name plaque like an NPC! I'll update as I meet more of my created sims outside of school and see if they show up the next day too! 🙂