@aaronrulz
You could save your game then take the townie’s household into manage households. It’s possible the townie could have the gloomy trait. Gloomy sims get sadness randomly. Or it could have to do with sentiments or lifestyles too influencing moodlets. If you take them into manage households to check and they are unplayed sims, don’t forget to put them back into the unplayed category. Also if they are a good sim and are around an evil sim that can cause sadness too. I don’t know if mean causes sadness to a good sim, but it might. If a family sim goes too long without being around family, I think that can cause sadness too.
@ryouma17 if you have higher school years you can dress a high schooler you are playing in a school uniform. You may want to put the school uniform in other categories as well, like cold and/or hot weather, as they may automatically change to one of those categories.
I’m not sure, but you might be able to find the school outfit for children in CAS too.