Hello! I'm just wondering why I can't follow my teen to high school. I've downloaded mods and may have gotten something not compatible with the High School Years pack. However, I was not able to find which mod is it. Have any of you encountered problems like this?

Remove all your mods. ALL your mods. (Do not remove any CC hair or clothes, otherwise all your sims with CC hair or clothes will end up bald and naked in the next step). Start your game and see if it works without mods. If so (probably no reason it shouldn't), then start all over again replacing mods no more than 2 or 3 at a time. Yeah, it's a pain in the ass -- it always is when it comes to finding a bad mod.