It just occurred to me: in addition to surveying the multifarious accounts of fallacies available in book form and on the web, your son might find a reasonably rigorous treatment of evaluating flesh-and-blood arguments useful. Could I then recommend Alec Fisher’s The Logic of Real Arguments (2nd ed.), Cambridge University Press. This book has been out for some time and so it should be possible to pick up a second-hand copy reasonably inexpensively.
