The expression of the woman in the famous portrait of Leonardo da Vinci is usually called enigmatic, but this Julia Roberts vehicle referring to the painting could hardly be described that way. To the contrary, “Mona Lisa Smile” is about as subtle as a sledgehammer. Some will call it “Dead Poetess Society.” Others will christen it “The Empress’ Club.” But the most appropriate alternate title for the college nostalgia trip would be “The Not-So-Prime of Miss Jean Brodie.” Though the character that Roberts plays–a UCLA-trained art historian who brings her progressive teaching methods to the staid, traditional environment of early-fifties Wellesley–is called Katherine Watson, she’s quite reminiscent of the protagonist of the Muriel Spark novel adapted into the 1969 showcase for Maggie Smith: like Brodie, Watson ruffles feathers with her unconventional views and her growing influence over the impressionable girls she teaches, and lots of troubles–administrative and emotional–ensue. The difference is that while Ronald Neame’s film boasted a towering central performance and at least touched upon some serious pedagogical issues (though hardly as well as the book does), Mike Newell’s merely gives Roberts an opportunity to repeat her familiar star shtick–she smiles broadly and stumbles a lot–while offering what amounts to little more than a period soap opera that makes the most simplistic possible observations about an era on the cusp of female liberation.

In the formulaic script fashioned by Lawrence Konner and Mark Rosenthal, Watson arrives at Wellesley, the all-girl Ivy League establishment whose well-to-do students regularly link up with Harvard men, for the fall 1953 term. She’s a spunky but vulnerable West Coast transplant who hasn’t yet finished her dissertation and is looked upon with suspicion by the snobbish department head because of her high regard for modern art; indeed, a secretary lets drop that she was hired only because the first choice–an applicant from Brown, no less–turned down the job and no one else was available. After being humiliated in her first class by the girls–among them arrogant brat Betty (Kirsten Dunst), porcelain princess Joan (Julia Stiles), reckless Giselle (Maggie Gyllenhaal) and mousy Connie (Ginnifer Goodwin)–who have virtually memorized the textbook and can identify every slide as soon as it hits the screen, Watson takes a different teaching approach by bringing up the apparently unheard-of question of what constitutes art and demanding that the students express their own opinions and justify them. She’s trying to get them to think for themselves (dammit!), and to become independent and assertive. But her noble efforts in this direction are hampered not only by the school administration (headed by haughty President Carr, played by grande dame Marian Seldes), but by the smugly self-assured Betty, who writes stinging editorials attacking whatever she considers “subversive” of the school’s traditional role of training wives for Harvard graduates, and who just happens to be the daughter of the institution’s most powerful alumna (Donna Mitchell). It’s inevitable that problems should erupt. The first comes over the progressive action of one of Katherine’s housemates, school nurse Amanda (Juliet Stevenson), in providing condoms to students–an action Betty condemns in print, leading to Amanda’s termination. But the more important arises from Katherine’s refusal to excuse Betty from classes after she weds Spencer Jones (Jordan Bridges)–a scion of the family that gave rise to the expression “Keep up with the Joneses,” we’re told–and from her encouraging Joan to place her own desire to attend law school over becoming a submissive housewife to her intended hubby, Tommy Donegal (Topher Grace). As if all this classroom friction weren’t enough, Katherine is having romantic problems, too. Will she be true to her California boyfriend, lovably middle-class Paul (John Slattery), or succumb to the roguish charms of Wellesley Italian prof Bill Duncar (Dunbar West)? To add to the tension, Bill has been bedding students, including Giselle, apparently the sole Jew among the girls and a kid driven to drink and flirtatiousness by the fact that–gasp!–her parents are divorced. And Connie, whom Betty sets up with a relative for a date, has her budding relationship with the geeky guy sabotaged by Betty herself, whose bitchiness seems to know no bounds.

This episode-filled but entirely superficial scenario clearly has enough material for several installments of a television soap, and that’s pretty much what we get here. There’s lot of incident but precious little insight; at one point a character says to Katherine, “You’re not saying anything–you never really do,” and the same observation might be made of the picture itself. Presumably “Mona Lisa Smile” wants to comment on the wife-and-mother role to which American society relegated women in the early Eisenhower years–a theme treated most crudely in the character of Katherine’s colleague Nancy (Marcia Gay Harden), a teacher of poise and elocution who happens also to have been rendered an alcoholic old maid as the result of having been dumped long ago by her intended–and, by the extension of the idea of “subversion,” on the whole repressive political atmosphere of the McCarthy years. But its observations never rise beyond the most simplistically melodramatic level. And when the script tries to add some complexity by challenging Katherine’s choices–questioning her desire for marriage and emphasizing Joan’s unwillingness to go along fully with her views on the matter–it simply muddies whatever message it wants to convey. The WASPishness of the Wellesley environment, moreover, is so archly rendered as to be pretty much a caricature; the institution should be credited for not protesting too much over a script in which it’s labeled “a finishing school disguised as a college,” but it probably should object to being shown, even in hindsight, as so clownish a place. (After all, this is the school that embraced as eccentric a personage as Vladimir Nabokov from 1941 to 1948.) Still, one has to praise the loveliness of the gauzily nostalgic vision of the campus created by production designer Jane Musky, art director Patricia Woolbridge and cinematographer Anastas Michos. Visually the picture certainly soothes the eye (just as Rachel Portman’s smooth score does the ear).

But even here there are problems. Set decorator Susan Tyson and costumer Michael Dennison have certainly worked hard at getting things to look right, but the result is rarely convincing–largely because one never escapes the feeling that the younger performers are merely playing dress-up. And this affects their performances badly. Stiles is beautifully decked out, but can’t be very expressive beneath her alabaster mask. Dunst is as authentically catty as anything out of Clare Boothe’s “The Women,” but even as fine a young actress as she can’t pull off Betty’s abrupt reversal of attitude at the close. Gyllenhaal manages the wild-girl stuff well enough, but the part is underwritten, and Goodwin does her fumbling wallflower routine nicely. On the male side, the personable Grace looks distinctly uncomfortable in preppy clothes and hoisting an oversized cigar, but he remains a pleasant presence; Bridges is suitably self-assured, though he too appears stiff in the period garb. The older players are more problematic. Roberts never manages to shed her modern mannerisms to create a credibly fifties character or to submerge her personality in favor of Katherine’s; hers isn’t so much a performance as a star turn. Hardin, a much better actress, is stuck vainly trying to breathe life into a cardboard figure that might have come out of William Inge or very early Tennessee Williams, and West and Slattery barely register. Seldes and Mitchell, meanwhile, lay on the hauteur too heavily as the ultimate snobs.

The mediocre work of the cast must be laid partially at the feet of Newell, who’s made good films in the past (including “Enchanted April” and “Donnie Brasco”) but whose direction here seems indifferent, even lax–as though he were ashamed of the cliches and unwilling to punch them across. The attitude might be understandable, but in this case it’s a mistake, making for a flaccid two hours that might at least have had some camp energy. Because “Mona Lisa Smile” is a highbrow title for an innately middlebrow picture. Fans of Julia Roberts or her young co-stars might enjoy it, but despite the paucity of lead roles for women in Hollywood nowadays, the lack isn’t enough to applaud the appearance of weak sisters like this.