Is there a way to change the age of a sim on sims 3?

my friend told me the way 2 stop ur sims from growin (aging off) but is there a way 2 change the age of a sim??? it waz just my sims b-day and i turned into a teen even tho im only supposed 2 b a kid. is there a way 2 make my sim switch from a teen 2 a kid???? and then after tht i will use aging off!?!?!??!?!??!?!?!?!?!