On the heels of the raunchy youth comedy "Porky's" passing the $100 million mark in rentals comes the announcement that you'll soon see a "Porky's" video game. And while playing it, you'll be able to sing along with the movie's six male leads, who are getting together to form a band . . . Meanwhile, several other studios are setting their sights on the huge audience for raw comedy that made "Porky's" such a hit. Cheech and Chong's "Things Are Tough All Over" opened strongly last weekend, even though it contains such unusual features -- unusual for Cheech and Chong, anyway -- as a coherent story line and long stretches without drug jokes. "The Pirate Movie" didn't fare so well. While its producer once boasted that the updated, pop version of "The Pirates of Penzance," with teen stars Christopher Atkins and Kristy McNichol, would become a huge youth blockbuster and steal the thunder from Joseph Papp's version of Gilbert & Sullivan's "Pirates" (slated as a Christmas release) the film has opened to dismal reviews and a paltry box-office take.

The most blatant high school movies, though, are yet to come. Walt Disney's "Tex" will be the first of three upcoming films based on novelist S.E. Hinton's tales of teens on their own; all three star Matt Dillon, an avowed Hinton fan. "Fast Times at Ridgemont High" and "The Last American Virgin" are rowdy, uninhibited tales of high school hijinks. "Fast Times" is slated to open tomorrow, and if nobody expects it to have a staying power equal to "Porky's," it does contain lots of little perks for teens in the know. It was filmed largely in the Galleria shopping center near Los Angeles, a spot already renowned for its prominent mention in "Valley Girl," the song by Frank Zappa and his daughter that has fostered the summer's biggest outbreak of new teen-age slang; it features Bruce Springsteen's sister in a small role; and when one character pulls up alongside a stunning blond in a convertible, she turns out to be rock star Nancy Wilson, lead guitarist in the band Heart. Heart, incidentally, wrote a song called "Fast Times" for the movie's star-studded sound track, but its record company wouldn't permit the band to give the song away since that would mean making money for a rival company.

"The Last American Virgin" also has a highly marketable rock 'n' roll sound track featuring the likes of the Police and the Cars. As one advance viewer says of the film, "You can tell that all the characters are supposed to be New Wave because they wear headbands." And the quality? "It's sleaze. A really dreadful exploitation movie about Hollywood high schoolers who save up all their money for prostitutes."