"Porky's II: The Next Day" recreates a day so crowded with activity for the irrepressible scamps of Angel Beach High, an apocryphal institution of practical joking located in Florida, circa 1954, that it actually takes several weeks for everything to happen.

But why pick nits off such a superfluous example of nitwit movie farce? When you get right down to it, the title of the new Ingmar Bergman film is just as dim as this one's, and the continuity just as ragged. It's also difficult to hold much against a "Porky's II" when encountered so soon after competition as hapless as "The Survivors" and "Yellowbeard."

Now at area theaters, this inevitable, expendable sequel to the lowbrow comedy sensation of spring 1982 reunites many of the original cast members in a scenario designed to blend raunch, romance, period flavor and social consciousness into a frothy brew that meets the racier expectations of the "Beach Party" public of the '80s.

In fact, the "Porky's" comedies, contrived by director Bob Clark and various screenwriting collaborators out of Clark's exaggerated recollections of a Fort Lauderdale teenhood, resemble a hybrid of the "Beach Party" series and Robert Altman's "M*A*S*H," which has also acquired a more juvenile patina as time has passed.

Clark has fiddled with the formula in a way that may be ill-advised. The original proportion of roughly 95 percent raunch to the rest of the ingredients has been evened out in "Porky's II." Social consciousness and cultural respectability are allowed to make deep inroads on the raunch, since the kids are suddenly congregated around the Drama Club and devote their major conspiratorial campaign to discrediting a bigoted preacher who threatens to interfere with the term play, "An Evening With Shakespeare," out of hostility to both the bard and a young Seminole in the cast. Gee, everybody is taking this back-to-basics stuff to heart!

Succumbing to a temporary attack of romantic solicitude, Clark indulges a long heart-to-heart talk that inspires tender rather than sniggery responses about the attraction between the sexually gauche Pee Wee (Dan Monahan) and the sexually experienced Wendy (Kaki Hunter), who reveals that she's not nearly as experienced as school legend would have it. This welcome change of emphasis might go further if it were sustained during the rest of the film, but having given Pee Wee and Wendy a basis of mutual interest that transcends mere slapstick horniness, the writers don't know what to do with their romance.

A pity, because the suburban showing I attended had such a curiously predominant percentage of adolescent girls that it would no doubt have paid off, in more ways than one, for the only girl in the story to have risen above her erstwhile identity as a pert pushover. The idea that modern kids are more knowledgable about sex than teens of earlier eras is surely contradicted by the attraction something like "Porky's II" holds for teeny-boppers. It underscores the fact that they only think they know more.

Unlike previous moviegoing generations, today's adolescents have relatively easy access to ostentatiously profane facetiousness, and perhaps the "Porky's" comedies succeed to some extent as smokers for juveniles, but even the ribaldry and misinformation they exploit is at least a generation out of date. "Fast Times at Ridgemont High" is the only recent comedy in this vein that also reflects a contemporary teenage culture.

Despite the new tilt toward highmindedness, Clark protects himself with elaborately vulgar gag sequences built around a practical joke on Pee Wee, a practical joke on Nancy Parsons as the hostile, tubby gym teacher Miss Balbricker, a practical joke on the rabid pastor and his redneck KKK buddies, and a practical joke on Edward Winter as a hypocritical, glad-handing city councilman who betrays the student thespians by caving in to the Forces of Reaction. However, Winter clearly has the last laugh, since he contributes a smooth-as-silk comic performance that illustrates how much technique the young leads--and their director, for that matter--haven't begun to master. PORKY'S II: THE NEXT DAY

Directed by Bob Clark; written by Roger E. Swaybill, Alan Ormsby and Bob Clark; director of photography, Reginald H. Morris, C.S.C.; art director, Fred Price; edited by Stan Cole; original music by Carl Zittrer; produced by Don Carmody and Bob Clark. A 20th Century-Fox release. This film runs 97 minutes and is rated R. THE CAST Pee Wee....Dan Monahan Tommy....Wyatt Knight Billy....Mark Herrier Mickey....Roger Wilson Tim....Cyril O'Reilly