Tips to make teenagers look more like teenager?

Clothing and hair is super important. Typically curlier and messier hair for teens. Also baggier clothes like hoodies sweat shirts etc.

Female teens don't get makeup in my saves except formal and party to help differentiate. Youd be surprised what the lack of makeup accomplishes aesthetically.

Higher voices and slimmer bodies including shoulders breasts and bottoms.

Ace abd braces help too.

Also, smaller jaw line, especially for men makes a WORLD of difference.