(FORTUNE Magazine) – American competitiveness is ailing because workers can't spell, do long division, or tell you who Sophocles was, right? Not necessarily, argues Peter Cappelli, an associate professor at the Wharton Business School. He has been studying the matter closely since 1988, when he was on a Labor Department commission that examined work force quality. Cappelli says the underlying trouble is really in poor employee attitudes, or what he calls a lack of ''work maturity'' -- that is, conscientiousness, ability to function without close supervision, respect for others, and a positive view of authority. ''Executives at the companies we studied weren't bitching about skills,'' he says. ''They said, 'We'll train workers if the schools can produce them with the right attitudes.' '' Indeed, he adds, good grades in school are a poor predictor of job success. AT&T, renowned for sophisticated hiring techniques, has found extracurricular activity a better gauge. So just what does a good work attitude look like? You see it when a plant employee, say, fixes or reports broken equipment even though it might not be her specific job to do so. Says Cappelli: ''You could say that, in part, it's what you do when nobody's looking.'' There's no easy solution, says Cappelli, especially now with cutbacks in the armed forces -- which he calls ''one of the greatest attitude adjustment devices around.'' (For more on teaching kids about work, see our Special Report.) While a company can create a culture that fosters responsible work attitudes, ''by then it might be too late -- we must start earlier.'' Cappelli just finished teaching the first year of a new work-attitude curriculum for MBA students at Wharton that he helped create, which includes classes in teamwork, managing work and family, and leadership skills. Even that's a bit late. Says he: ''It's easier to teach a sixth-grader about teamwork than it is to teach a college-educated MBA student who has had individualism stressed by years of protracted schooling.''