I have the same issue with school. Kids go to school, but remain outside, any attempt to enter the door fails, as does trying to attend a painting class. My school lot is currently set to "No Visitors allowed", where as most rabbit holes do not have a community lot type, that is the only difference I . I also tried replacing the school building and changing the lot type to something else such as "Visitors allowed", without luck.
I'm wondering if there is there a way to reset lot type, as School or rabbit hole isn't available in the drop-down.
I was having the same issue. I moved the school building back a little (very little) then saved to library. I then bulldozed the original school. The lot seemed to be set to no visitors so I changed that, replaced the building and my sim was able to attend painting class. I wanted to test it with a kid going to school but I found I could no longer change households so closed the game and will restart and test with a kid.
I noticed that the sims that tried to go into school got the "route failed" balloon above them.
I managed to enable painting classes, i need to wait 1 more day to see if my adolescent sim can go to school, but i think i fixed it. I removed the school, then i used the SLEDGEHAMMER TOOL in the entire area that the school was.
There was some invisible object which i deleted, and i think that was the problem... Still needs confirmation, i'll edit this post soon.