I'm not being facetious when I say that Summer School remains the crowning achievement on Mark Harmon's résumé. Fans of '80s teen comedies think it's too tame nary a breast is exposed, hardly a swear word uttered but I've always admired its shaggy, what-the-hell vibe. The whole thing's a perfect storm of casting and creativity: Aside from Harmon's obvious ease in the role of layabout teacher Freddy Shoop, School just out in a ''Life's a Beach'' special edition (PG-13, 97 mins., 1987) coasts on the hysterical chemistry between the nine young actors who played his underachieving remedial-English students, a knowing script from a 26-year-old screenwriter, a corny ending that copies From Here to Eternity yet still feels original, and Kirstie Alley's saucy turn as the one woman Freddy can't charm. Films this breezy don't typically lend themselves to major DVD extras, but Harmon lets loose a few interesting secrets in his commentary track with director Carl Reiner, helpfully pointing out the onscreen moment when he broke his shoulder. And in a making-of featurette, we learn that Alley beat out none other than Fran Drescher for her role. Now who's laughing through her nose?