First off the book Johnny Tremain is both one of the greatest children stories and one of the greatest revolutionary war novels ever written. Published during the Second World War it has never gone out of print since and rightly so. As source material it is perfectly suited to be given a movie adaption. And when the movie sticks to following the book it is rather entertaining in a 1950s Disney sort of way.
The first half hour is close enough to the book to entertain the fans. The character of Johnny has been changed from arrogant and cocky to pure and innocent in the best tradition of Disney films which can hardly come as a surprise but to expect anything else out of a kid's movie is to be let down. The second half hour loses the mood but keeps near the plot. The Boston Tea Party is entertaining although the singing after it is unforgivably Disney. But by the last half hour the book is thrown to the winds as we see the war first hand. Something about seeing laughing children dancing around the countryside shooting at redcoats struck me as kind of disturbing for a Disney film. Obviously war was a great adventure that people could enjoy in a typical '50s fashion where nobody but the bad guys got hurt and everyone could share a nice drink afterward. Oh, and somebody who is supposed to die, whose death gives the entire book meaning, doesn't. That would be too dark for a Disney film.
Now if I thought that any of those additions were beneficial to the movie I couldn't really complain but none of them worked. The first battle was alright but the psychotic killing kids having fun was just awful. The producers probably couldn't see why this might be considered 'creepy'. The acting from the lead is awful and he doesn't seem to have been in anything else afterward. The guy playing Rab seemed to bring a little of the distant charm described in the book but the script doesn't give him more than one or two moments. Walter Sande as Paul Revere was good as were a few of the founding fathers but nothing to write home about.
On the plus side the sets are marvelous. I've never seen colonial Boston come to life so well since, largely due to an absence of Revolutionary War films. The Battle of Lexington is moderately well done rather obviously leaving open the question of who fired first. And the first half hour entertains. So in conclusion: good book, good sets, bad everything else. Remake anyone?