Please use this thread going forward: Teenager don't get third trait on aging/no Graduation | EA Forums - 4948331
This happened to me too. I don't use mods. Here's a link to my save file before I aged my two oldest adult teens up.
https://drive.google.com/file/d/14an8IBF-DptJrOyejRl0S3T6BTGhKBMW/view?usp=sharing
I have to ask, because I provided EA with a detailed report on what's happening and they ignored it, but are you aging your sims up on SUNDAY? I have found that through my testing on this bug that any teen that ages up on Sunday will have this issue. I experience this issue with no mods installed, but with MCCC installed it solves the problem of the missing trait. However, you may notice that you are not gaining character values. There is a an issue with the coding dealing with the high school pack which is causing this issue. It's due to hastily putting out scripts before they are tested. I have determined that EA has no test environment, We are their testers. We are the team that finds and reports bugs. We should be getting PAID to do this for them. I've already offered my services as a retired DBA. I would bet my life that I could do a much, much better job at finding issues than what EA has been doing.
Again, confirm the day of the week, as most likely it is Sunday that's causing this issue.
See this:
