Released on DVD today is “High School Musical 3: Senior Year,” the end of a tween era that began humbly enough on the Disney Channel in 2006 with “High School Musical,” a dorky, intentionally retro little show about a high school basketball jock (the slight, fey, improbably cast Zac Efron) and a math and science whiz (and therefore equally hugely-improbably cast Vanessa Hudgens) who find true love and musical fulfillment singing with their peers in the school’s musical.

That first movie made more money in six months than the Cali drug cartel makes in a year, and so Disney set up an extraction refinery over the site and began pumping. Pens, stationary, folders, backpacks, karaoke sets, dolls, pimple pads, socks, tube-socks, a clothing line, and buried somewhere in all that, a second television movie, 2007’s “High School Musical 2.” The two stars (having meanwhile been ordered to date each other and having been vetted for an older marketing group with separate, non-threatening, low-grade scandals – him in photos kissing another boy, her in photos wearing nothing at all) returned, as did the supporting cast, including Corbin Bleu as afro’d basketball star Chad Danforth, Ashley Tisdale as the rich, spoiled Sharpay Evans, and pouty Lucas Grabeel as her henpecked brother Ryan.

Even to fans of the show, “High School Musical 2″ felt derivative, but “High School Musical 3: Senior Year” escapes that in the only way possible: nostalgia. Our stalwarts are graduating, heading off to different schools and different lives, and they want one last romp on the boards before they go their separate ways. The major difference here is scope, since this is the only show of what we must now call the trilogy that was produced as a theatrical release; director and “HSM” mastermind Kenny Ortega knows he has a bigger venue, and he fills it expertly – the songs are catchier, the production numbers are bigger, and the cast – always remarkable for their synergy – here works in perfect unison. The jokes are actually funny, the timing is spot-on, and the rousing conclusion (to the infectious notes of the first movie’s feel-good anthem “We’re All in This Together”) will please all but the most jaded twentysomethings.

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“HSM 3″ makes rather obvious gestures in the torch-passing direction, and no doubt there will be a “HSM 4.” But by then this fantastic core cast will have gone on to other things – Efron (rightly or wrongly the show’s one big breakout star) playing a series of romantic/action leads (”Johnny Quest” is rumored) while yearning for a “serious” acting career that never happens, Hudgens playing ingenues until she’s on the shaded slopes of 50, Grabeel taking one for the team with the requisite drug overdose, and Tisdale (by a wide margin the cast’s best performer), if there’s any justice, owning Broadway for the next century.

Not that the pitiless, sharklike tween audience will have noticed. They’ve already forgotten “High School Musical” – indeed, the Jonas Brothers are already passe; all iPhones are tuned to Nikelodeon’s “Spectacular!” and the improbably cast hunkette of the next fifteen minutes. You might as well learn the name now: it’s Nolan Gerard Funk.

Steve Donoghue