There seems to be an issue with HSY. Most of the teens don't grow up they just stay as teens forever. I have multiple generations when go to school I see the same students from previous generations. The reason I got HSY so that my teen can find a partner there while being a teen. Even if you find a partner you can't get married cause they never reach young adult and you see the same students all the time from every generations.
@LascusClyne
I noticed that too.
This is because Teenagers are not in the World. That‘s why they don‘t age.
Are you going all the way to graduation where you get the graduation ceremony or are you graduating your sims early? In my game, I found that if you graduate early, you keep the same NPCs in high school the next time. But if you keep your sim in high school until they reach the end of the teen life stage or age them up early with a cake, then you get the graduation ceremony with its graduation pic and that one or two of the NPC sims will graduate with you at the ceremony and become young adults. The NPC aging setting doesn't matter in this case. That doesn't hold true though for the teens used as NPCs like Molly, Ash, Kevin, etc. if they are marked as played or any other teen you have in a played household.
Hope this helps.
I am not sure what the difference is between those first sims and the later ones. One thing I can think of is the aging switch. I assumed that you are talking about the game generated NPCs.
Are you playing with aging on for NPCs?
Have you changed that setting between the time the first sims aged up and the later ones? That could account for them not aging.
However, I have noticed that a change seems to have happened after HSY was released. The first batch of NPC students I had were in the "Other" tab of Manage Household while the ones that came after were hidden. Hidden sims don't age for the most part. All my NPC high school students are in hidden now. Many are children of the JA skeletons for some reason. The ones I have show that aging is disabled for them so the only way to get them to age up is to move them into an active household via the Ask/Invite to Join Household option. That changes their aging, so they age like played sims.
Hope this helps.
