Here’s what their website says:
“The Statue’s Crown can only be accessed by climbing 162 stairs. There is no elevator service to the Crown. The climb is strenuous. The National Park Service recommends that crown visitors have no significant physical or mental conditions which would impair their ability to complete the climb”
“Children must be at least 42 inches, or 1.1 meters, tall to visit the crown. Children cannot be carried. It is the responsibility of the parent or guardian to ensure their child meets this requirement. Children smaller than 42 inches (1.1 meters) may only ascend as high as the top of the Pedestal (observation deck). ”