Some five year olds are ready for this -- many five year olds would find the concept of saving 200 pennies a bit beyond them. David wanted an electric train and staged a scene when he didn't get one. So his parents put it up to him to prove his fitness for such an expensive toy by earning 200 pennies towards it. And they stuck to their resolve even at the last moment when there's a good deal of tension and anguish as David breaks a mirror and fears for the loss of his hard-earned cash. It's an unusual plot for a book for small children, but- properly handled- has a very constructive value. Vera Nevelle pictures in line are appropriate to the text.