"Freaky Friday," now at area theaters, suffers from sluggish exposition mediocre direction and a one-closeup-after-another method of composition advertising the film's eventual retirement to the Disney TV series, but it probably salvages things with juvenile audiences by finishing fast.

The hectic slapstick conclusion, alternating car chase and demolition stunts with water-skiing stunts, appears to persuade kids that they've had a swell time, even though the bulk of the picture leaves them silent and fidgety. In a cynical mood one might almost interpret it as a king of basic training film, designed to prepare children for the level of consistency that conventional movie and TV producers feel safest with: sustained blandness relived by gratuitous thrills.

The source material, a sprightly 1972 novella by Mary Rodgers, who also receives credit for the screenplay, was once acquired for Barbra Streisand, who might have extended her comic range - and avoided "For Pete's Sake" - by trying to develop the turn about premise of "Freaky Friday," in which a mother and teen-age daughter miraculously exchange bodies and roles for 24 hours. Barbara Harris and jodie Foster are scarcely conventional choices for the leads, especially in a Disney production. Their skill and quirkiness put a little distinction into the genrally uninspired, hand-me-down situations selected to show mother making a wreck of school and adolescene while daughter makes a wreck of housekeeping and adulthood.

Nevertheless, Harris and Foster are fighting a losing, uphill battle against predictability. Gary Nelson seems to direct movie comedy as if he were following some outdated laugh-by-the-numbers kit. Moreover, Harris and Foster never really harmonize as mother-and-daughter. There's no way to capitalize on the joke that the actresses themselves suggest - the daughter may be more mature than the mother - because the point of the story is exactly the opposite.

Harris is a grown-up actress who has always seemed peculiarly child-like and out-of-it. Foster is a juvenile actress who has always seemed remarkably mature and with it. By all rights they should find it easier to cope with their post-turnabout identities, a possibility that couldn't have occurred to Mary Rodgers when she was writing the novel, which is sensibly intended to remind parents and kids that neither generation has it as easy as the other likes to pretend, particularly during family squabbles.

Kaye Ballard makes a brief, ellivening appearance as a girls' hockey team coach who looks and sounds like Vince Lombardi. Her opposite number is Ruth Buzzi, so this sporting rivalry suggests riper possibilities than the filmakers have been prepared to harvest. John Astin is such a pitiful throwback to TV dumb-daddyhood in the oblivious role of Harris' husband and Foster's father that you begin to wonder why he wasn't simply thrown out. The location of the novel has been shifted from the upper East Side to Southern California suburbia, presumably to correspond with the Disney studio's view of the upper-middle-class dream life shared by the vast majority of the audience.