when a pc ages, it gets penalties to physical stats and bonuses for mental stats.
what are the penalties for being an adolescent or child?
I am not aware of them being listed anywhere.
If I had to low stat someone, I would reduce wisdom first, then probably strength for teenagers.
Charisma could be reduced as well.
Age16-18 -1 Wis -1 Str -1Cha
Age13-15 -2 Wis -2 Str -1 Int -2Cha
Age9-12 -4 Wis -4 Str -4 Int -2Cha
and so on if you really want stats for kids
Not completely happy with those penalities, but there you go.
d20Modern gives children (up to 11 years old) -3 to Str and Con and -1 to all the others. At 12 and up, no modifiers.