When Sims die Kids reset at Schoolbus

As mate54 mentioned, there was a bug that would sometimes happen even in the original game, where if there were no parents they would try to do the "report card cheer" and error out instead. My suggestion is to get rid of that interaction altogether and see if it solves the problem. The hack I have is from Mod the Sims and will pop up with a search of "Report Card Fixes." 

Try send them to vacation , and tell me if fix it

I just had the same bug. I was playing with mods and I was trying to make a family survive without parents as a challenge but then I noticed that both the teen and the child never came home with homework. So I tried removing my mods and I had the same result.

I had the same experience but without losing school points, detail that I had used cheat to change the name of the child sim. I made my sims go on vacation, and when they came back it didn't bug anymore

Yeah, there are no living parents anymore, but the grandparents are still alive.

I wouldn't mind so much, if I couldn't loose the child because when their grades get bad the social worker will take them away.

Lelana87 Can you confirm that they have no living parents (you mentioned one Sim dying, so I'd just like to clarify)?

Sounds to me like they are trying to do the interaction where they cheer with a good report card, but have no parent to show it to. You can post the error you get (with testing cheats enabled) just to confirm, but this is a bug that carried over from the original release.