A love letter to rock music and the driving force to never give up your dreams, "The School of Rock" is the biggest breath of fresh air that has happened to mainstream comedies in years. Exuberantly written by Mike White (2002's "The Good Girl"), directed by Richard Linklater (2001's "Waking Life"), and acted by everyone involved, it is a joyfully simple and exceedingly entertaining motion picture that is about as much unadulterated fun as you are likely to have at the movies all year.

For as long as he can remember, Dewey Finn (Jack Black) has had no other goal in life than to become a rock-and-roll superstar. When he is abruptly fired from his band and in desperate need of money, Dewey finds himself posing as his pussy-whipped roommate Ned Schneebly (Mike White) and going to work as a fifth grade class's substitute teacher at Horace Green Prep. Dewey is not much of a teacher in academics, but when he discovers his students' musical talent, he promptly elects them as his new band and turns each class into a secret rehearsal session leading up to a Battle of the Bands competition. In the process, Dewey finds himself befriending the kids and teaching them the most valuable lesson of all: to be yourself.

The premise is straightforward and makes no promises of being life-changing, but "The School of Rock" is an absolute delight from start to finish, so much so that you hate to see it end. Its running time of just under two hours flies right by and, amazingly, there isn't a dry spot or failed joke to be had.

The key to the film's success is the marvelously winning bond between Dewey Finn and the kids, all fifteen of whom are written with such care and attention to detail that they claim their own individuality. Jack Black (2001's "Shallow Hal," 2002's "Orange County"), always very funny and with actual dramatic range and honesty in every role he takes, is a comedic genius. There is no other actor working today quite like him, and his freshness and grungy magnetism are a genuine treat. As he bonds with the kids, there is an affection between them that jumps off the screen and feels real, undoubtedly because it is. The children, most of whom are first-time actors, stand as one of the most all-around natural and likable young ensembles in memory. Standouts include Miranda Cosgrove as band manager Summer; Joey Gaydos as lead guitarist Zack; Kevin Clark as drummer Freddy; Rebecca Brown as bass player Katie; and Brian Falduto as band stylist Billy.

In the sort of sparkling supporting role she is known for giving, Joan Cusack (1999's "Arlington Road") is perfectly cast as uptight school principal Rosalie Mullins, whom Dewey encourages to let out her inner Stevie Nicks. Cusack brings depth and allure to a part that could have been a throwaway, but isn't. In one delightful scene, Dewey invites Rosalie out for a drink and she ends up getting lost in Stevie Nicks' "Edge of Seventeen" on the jukebox. Cusack deserves a supporting actress Oscar nomination; she is that good.

Last week, a similar motion picture was released called "The Fighting Temptations," in which Cuba Gooding Jr. led a church choir to victory at a climactic music competition. It was strictly by-the-numbers, save for its musical sequences, and the characters were so thinly drawn as to be practically nonexistent. "The School of Rock," which ends at the Battle of the Bands contest, one-ups "The Fighting Temptations" and shows that enormously inferior effort how to do this sort of story right. Every once in a while a movie comes along that, upon first glance, has no right to be so utterly charming and just plain great. "The School of Rock" is such a film, and it earns that right every step of the way. It is alive, both in its razor-sharp comedy and its rock-solid music. Don't miss it.