"I knew you were a kid." Bruce cuts you off when you were trying desperately to lie and hide the truth. However it's no need to lie. Bruce knew it from the start that you were a kid turned into an adult by your powers. Just like Shazam. "I won't tell the Leaguers, don't worry." He reads the worry on your face and tries to reassure you. He doesn't care about your age, he already has the experience with working along side kids.