Examples:

• Stop being childish and act your age.
• Our 12-year old refuses to act her age and continues to suck her thumb.
• Would you two please act your age and stop carrying on in the middle of class?
• Come on, act your age! That food is for eating not for playing with!
• I need a vacation. At home, I have three boys under the age of six, plus my husband refuses to act his age.
• You need to grow up and act your age!
• I'm glad that Sarah is so committed to her studies, but sometimes I wish she would act her age and go out with her friends a bit.
• My grandchildren act their age with us and then go back home and make their parents' lives living hell.
• Stop being silly and act your age!
• Really, Neel, act your age a little. You're like a child sometimes!
• My son never acted his age. He always behaved like an adult until he got married.