The best Martin-Lewis collaboration is, to me, Hollywood OR BUST, but this one is not so far behind.
It has some hilarious spoofs of Chaplin's GREAT DICTATOR (the sequence where Mussolini and Hitler are on a barber's chair); NORTH BY NORTHWEST (the sequence in the train where Lewis is in Lynn's room), and of THE MAJOR AND THE MINOR, but, above all, Lewis is in great form playing an 11-year-old kid on the run from murderer and diamond thief Raymond Burr (fresh from playing the evil Thorwald in Hitchcock's REAR WINDOW the previous year).
I reckon Martin was a better actor than Lewis, but his part is less eye-catching. He sings two or three songs, but they are not the best in his career repertoire - quite forgettable, in fact - which does not do him any favors. One sequence where he is supposed to conduct a choir and Lewis takes over pretty much symbolizes Lewis' upper hand throughout YOU ARE NEVER TOO YOUNG.
Diana Lynn is attractive enough in her part, Burr is quite good as the heavy, and the rest of the cast is hardly perceptible.
Taurog's direction is purely commercial with some great action sequences, especially the final ski and boat chase; color photography is quite good for a 1955 low budget movie; and the script is good enough to keep you interested.
A well deserved 7/10.