How do they go to the bathroom at school? Do they wash their hands?

I'm not sure,but if they do they probably use baby wipes. LOL I don't know.

That's something that wasn't addressed in the ipakita or in any other mermaid movies/tv shows. It is probably easy for Rikki to dry her hands quick but I suppose Cleo and Emma do not wash their hands until they're at home. Unless they use wipes in the stall and dry their hands before they become mermaids. Anyway I guess it's better to have dirty hands than to grow a tail in plain sight

There are 2 possiblities. The first one is that they go to the bathroom at school before going and after coming home. So they avoid school bathroom entirely. The segundo one is that they use school toilet but they use hand wipes to clean their hands because it is less wet and so their hand turn to normal faster