NECESSARY PARTIES PUBLIC MEDIA VIDEO (800-826-3456) $29.95; 109 MINUTES; AGES 8 AND UP

Never underestimate a teenager with a mission. That's the lesson a suburban New York couple learns the hard way in this adaptation of Barbara Dana's 1986 novel Necessary Parties. Everything about this 1988 production feels just right, from the music and lighting to the casting and camera work. As the story begins, Stephen and Connie Mills are about to call it quits after 16 years of marriage. When Stephen (Geoffrey Pierson) awkwardly breaks the silence of a tense family dinner to announce the impending divorce, their 14-year-old son, Chris (Mark Paul Gosselaar), angrily declares his intention of stopping it. Neither Stephen nor Connie (Julie Hagerty) pays heed to him, so he is left to devise a plan to keep the once-happy family from crumbling around him and his 6-year-old sister, Jenny (Taylor Fry). Chris gets in touch with Archie Corelli (Alan Arkin), a part-time auto mechanic, part-time lawyer, and full-time character. At home, Archie warms his socks in the oven, plays baroque music (by Corelli, of course) on the recorder, and keeps Parmesan cheese in a corner of the kitchen, right behind the antifreeze. Archie is reluctant to take the case. ''Lawyers don't stop divorces,'' he tells Chhis. ''They like 'em. They're lucrative.'' Gosselaar exudes a relaxed confidence as the troubled but determined teen, while Arkin, magnetic as always, is superb-funny one moment, full of emotional energy the next-as he fights to keep Chris' family together. Author Dana, Arkin's wife, delivers the perfect mix of love and hardheadedness as Carol, Archie's adoring and strong-willed girlfriend of 12 years. Donald Moffat is convincing as the cantankerous Grampa Mills, an eccentric living on a houseboat. Fast-paced, witty, and powerful, Arkin and Dana's teleplay will provoke strong feelings in anyone touched by divorce. There's some sermonizing here, to be sure, but it's understated-and it's right. A

BACK TO THE FOREST JUST FOR KIDS (800-445-8210); $24.95 75 MINUTES; AGES 3 TO 7

Into the woods-and out of sorts. In this irritating story of people versus animals, nastiness reigns. There's greed. There's revenge. And, finally, there is an uneasy-and unsatisfying-peace. When a group of farmers intent on getting rich decides to chop down all of the trees in a nearby forest, the animals that live there try to head them off- writing letters, trying to gnaw down the bridge to the forest. Nothing works. Then they persuade the farm animals to trade places with them. When the ! farmland is overrun with wild forest creatures (boars, rats, bunnies), the farmers are ready to negotiate a truce. Though the dialogue does carry the story forward, it's clumsy, thoughtless, and grating. I stopped counting the number of times a character said, ''Shut up, you idiot!'' or ''You shut up!'' The animation is stiff; little care was given to faces, so no matter what characters are saying, the expressions are the same. Only the mouths (and sometimes the eyebrows) move. The background music ranges from annoying to unnoteworthy. And the voices are oddly unsuitable for the characters-one sturdy old woman has the clear, refined voice of a Julie Andrews -and all the characters speak in an aggressive monotone like that of an impatient parent trying to get through a bedtime story. ''You can turn this off now,'' said my 6-year-old, before the tape was over. F

CAITLIN'S HOLIDAY BY HELEN V. GRIFFITH; ILLUSTRATED BY SUSAN CONDIE LAMB GREENWILLOW, $12.95; AGES 6 AND UP

What if a Barbie doll could walk and talk-would she really be the kind of friend a young girl would want? Or would she narrow her violet eyes and snap things like ''I need to work on my tan'' and ''I wouldn't be caught dead in these (clothes)''? Caitlin, an ordinary little girl who has swapped her beloved old doll for a glamorous fashion doll at a resale shop, is shocked, and understandably mesmerized, when the 12-inch plastic figure, named Holiday, begins to talk to her. Alas, the gorgeous Holiday turns out to be a brainless snip, a clothing- obsessed narcissist who drives Caitlin crazy with her demands for expensive new outfits. Instead of playing or being a true friend, she just wants to shop and do her aerobics. Helen Griffith's hilarious satire combines the old-fashioned allure of a ''toys-come-alive'' story with an up-to-the-minute spoof. The prose is brisk and lively and the character of Caitlin provides a solid and believable ground for the fantasy. The only disappointment is that the little girl makes peace with her crabby little fashion victim instead of smartly throwing her out the window. A