With youngsters back in school, satiated by the usual overflow of mindless summer entertainment, the fall movie season traditionally turns to more adult fare, particularly high caliber dramas destined for Academy Award consideration. This season, social comment, which has not been in strong supply in recent years, makes a return to the screen with such subjects as armed hate groups, infanticide, political protest fugitives, as well as another look at the Vietnam War. Already playing in the nation's theaters is ``Betrayed,'' a drama starring Debra Winger and Tom Berenger about the right-wing underground in the Midwest. At the other end of the political spectrum is Sidney Lumet's ``Running on Empty,'' with Christine Lahti, Judd Hirsch and River Phoenix. The movie concerns a family of 1960s radicals who have been living underground and on the run for 15 years. ``Bat 21,'' with Gene Hackman and Danny Glover takes another hard look at the Vietnam War. ``The American movies of the 1930s and 1940s made a big impact on me because of their social content,'' says Costa-Gavras, the Greek-French director of ``Betrayed'' and other political films, including ``Z'' and ``Missing.'' ``When I first saw `The Grapes of Wrath,' it made an indelible impression on me. I deplore the fact that Hollywood retreated into a dream world in the last few decades. But I see hope for the future. There are too many young and talented filmmakers who want to comment on the world's ills.'' Social commentary won't be the only significance of the autumnal movie season. Following a record summer at the nation's box offices, Hollywood anticipates a rousing fourth-quarter finish to what may be its biggest box-office year. ``No Drought at the Box Office'' bannered the trade paper Variety in predicting a record $1.65-billion theater gross for the summer. With ```Crocodile' Dundee II,'' ``Coming to America'' and ``Who Framed Roger Rabbit?'' breaking the $100 million barrier and ``Big'' well on its way, chances are good that 1988 will top last year's $4.25 billion. The 22-week Hollywood writers strike apparently will not affect the supply of films to the world's theaters. ``There is an abundant supply of product,'' said Herb Steinberg, spokesman for the Alliance of Motion Picture and Television Producers. ``The Christmas pictures are in the can, and films now in production will carry into next year. And there are plenty of scripts ready to be filmed.'' Cheryl Rhoden of the Writers Guild of America acknowledged that the strike ``slowed some projects down.'' But she said the effects of the walkout on theatrical production are harder to measure than television, where the fall season was decimated. Fall movie-goers may notice a few more rough edges than usual because the numerous script revisions normally made in the course of theatrical filming were not permitted during the lengthy walkout. Here's what else is on tap for the fall season: Having little success in comedies, Whoopi Goldberg returns to drama with ``Clara's Heart,'' directed by Robert Mulligan (``To Kill a Mockingbird''). Meryl Streep is accused of murdering her baby at an Australian court trial in ``Guilty by Suspicion.'' Diane Keaton returns to drama in ``The Good Mother,'' directed by Leonard Nimoy (``Three Men and a Baby''). ``Criminal Law'' stars Kevin Bacon in a story about a serial killer. Jeremy Irons plays twins in ``Dead Ringers'' with Genevieve Bujold. Burt Lancaster plays a grandfather whose family visits him in ``Rocket Gibraltar.'' Clint Eastwood directed his homage to Charlie Parker in ``Bird,'' with Forest Whitaker (``Good Morning, Vietnam'') as the legendary sax man. ``Imagine: John Lennon'' traces the late Beatle's stormy life in rare footage from his estate. Hard to believe, but the musical will make a comeback _ sort of. Gregory Hines will appear as a dancer seeking help from oldtimer Sammy Davis Jr. in ``Tap.'' ``Heartbreak Hotel'' is listed as a musical drama starring David Keith and Tuesday Weld. Animation fans will be able to see two new features this fall: Disney's ``Oliver and Company,'' a reworking of ``Oliver Twist'' with the voices of Bette Midler, Billy Joel and Huey Lewis; ``The Land Before Time,'' a prehistoric family adventure from Steven Spielberg and Don Bluth, who combined on ``An American Tale.'' Since comedy is still king, there will be plenty of laugh-seekers in the fall market. Peter O'Toole, Steve Gutenburg and Darryl Hannah appear in a comedy-fantasy about a haunted English mansion. ``Heart Break Dance,'' a comedy-drama about family life in a New England town, marks Don Johnson's emergence in feature films. He stars with Susan Sarandon and Jeff Daniels. ``The Accidental Tourist'' reunites the crew of ``Body Heat'' _ William Hurt, Kathleen Turner and writer-director Lawrence Kasdan _ in a comedy about a travel writer and a dog trainer. Rebecca deMornay plays an FBI trainee who goofs up in ``Feds.'' Sally Field and Tom Hanks are would-be standup comics in ``Punchline.'' Michael Caine and Ben Kingsley play Sherlock Holmes and Dr. Watson for laughs in ``Without a Clue.'' In ``Moon Over Parador,'' Richard Dreyfuss appears as an actor who impersonates a Caribbean dictator. Want some adventure? ``Gorillas in the Mist'' features Sigourney Weaver as the ill-fated student of ape behavior, Dian Fossey. And Don Ameche and friends are back in ``Cocoon: The Return.'' In the action line, Mel Gibson, Michelle Pfeiffer and Kurt Russell appear in the drug-war ``To Kill a Sunrise.'' ``The Beast,'' with Jason Patrick, concerns a Soviet tank crew in Afganistan. In ``Last Rites,'' Tom Berenger portrays a Catholic priest who protects a girl marked for death by the Mafia. ``Alien Nation'' casts James Caan, Mandy Patinkin and Terence Stamp in a sci-fi cop thriller. All these films come from the eight major releasing companies. Many others will be emanating from the ever-growing independent companies.