CATHOLICS are hot. Nuns are on"Donahue." And now "Porky's" goes parochial in "Heaven Help Us," and that's a blessing.

This ensemble comedy, with its fine cast and clever writing, has more mass appeal than the conventional coming-of-age caper. The plot, though scattered, is tried and runs true.

Basically, an engaging gang of kids of various sizes, shapes and sexual appetites rebel against adult corruption. What makes "Heaven" best, though, is how well it evokes an era, an age and an ethnicity. Ah, to be Irish and 16 in the '60s again.

Matt Dillon's kid brother Kevin, the mugwumpish Malcolm Danare and the low-key Andrew McCarthy costar as star-crossed classmates in a baroque boys school in Brooklyn circa 1965.

McCarthy, as a quiet newcomer to St. Basil's, befriends Danare, as a chubby outcast, basically because there'no place else to sit in the cafeteria. Dillon and a couple of his cronies call them faggots, but the fussy intellectual Danare explains, "He's only projecting his doubts about his own sexuality."

Danare, last seen opposite a jealous Plymouth Fury in "Christine," has the best jokes, but Dillon has the best scenes, particularly on line at the confession booth, where the priest metes out Our Fathers and Hail Marys like Big Macs and fries.

Writer Charles Purpura has spilled out a lot of anger at the system, the religion, his childhood and the unjust teachers that we all had, and some of us still do have. Brother Constance (played with a zealot's glee by Jay Patterson) would bring back the Spanish Inquisition if he could. He's a sanctimonious sadist hiding behind the school system headed by an oblivious brother -- Donald Sutherland is carefully absent-minded in this thankless role.

The acting is sound all around, including a wild-eyed performance by Stephen Geoffreys as a boy in a losing bout with his new hormones; and by Washington's own Gonzaga High School graduate John Heard, as the good priest Brother Timothy -- the new order over the old.

Director Michael Dinner, who won praise for his television film "Miss Lonelyhearts," has a sound comic touch and a feel for characterization that keeps his debut film from faltering, though some of its scenes fail to come to fruition. This one time, he gets special dispensation.

I can't wait for "Fast Times at Immaculate Conception."

HEAVEN HELP US (R) -- At area theaters.