Too Young to Kiss (1951)

Eric Wainwright (Van Johnson), a busy impresario, is besieged by hordes of wannabe concert stars, eager for their big break. One of them is Cynthia Potter (June Allyson), a talented pianist... but she can't get in to see him. When she learns that Wainwright is auditioning young musicians for a children's concert tour, Cynthia dons braces and bobby sox and passes herself off as a child prodigy.