Early in filming, an insecure Robert Tsai approached director Richard Linklater and tried to talk him out of letting him be in the film because he felt he wasn't right for the part. Linklater responded that it was his very insecurity that made him exactly right for the part, and kept him in.
Miranda Cosgrove, who plays Summer in the movie, can sing. She took about a 45-minute "bad singing" lesson to sing horrible for the song "Memory" when Jack Black's character was looking for backup singers.
When asked for his opinion about testing from the other teachers, Jack Black dodges the question with song lyrics including the line "Let the children's laughter remind us how we used to be". One of the teachers asks if it is from a song, but he denies it. They are in fact from the song, "Greatest Love of All".
The big posters in Dewey's bedroom are of the The Sex Pistols, The Who, and New York City rock band Evil Jake. They were included because set designers photographed lead singer Mike Jacobs' apartment as research on how struggling musicians actually live, and Dewey's apartment is partially modeled on Mike's.
The idea for the movie came when writer Mike White moved into an apartment next to Jack Black. White would often find Jack Black running naked through the halls or blasting much of the music featured in the movie at full volume.
The rock band Led Zeppelin are notoriously hesitant to allow their music to be licensed for commercial purposes. Knowing this, Richard Linklater filmed a plea by actor Jack Black in front of 1,000 screaming fans, imploring the band to let the production use the "Immigrant Song" in the movie. The plea worked and the filmed request is included on the DVD.
The original screenplay was called "The School of Rock", and it was later shortened to "School of Rock". However, the opening credits had already been designed and partially shown in theaters with the word "The" in the title. Director Richard Linklater decided not to digitally remove the extra word from the credits.
The riff of The Darkness song "Black Shuck" is used in the film, but "Growing On Me" appears on the soundtrack. This is because Black Shuck contains the line "Black Shuck, that dog don't give a fuck" repeatedly.
Although the children in the film are supposed to all be the same age, the child actors ranged in age from Kevin Alexander Clark, who was nearly 15 by the time of the film's release, to Miranda Cosgrove, who has just turned 10 by the time of the film's release.
Dewey's nickname for Freddy the drummer, "Spazzy McGee", is a reference to an early draft of the character in which Freddy is a spastic sufferer of Attention Deficit Disorder (ADD) and can be seen taking Ritalin during class.
All the kids really play their instruments, and the backup singers are real vocalists. Jack Black also played a bit of guitar in the movie (for example, when he is teaching "Smoke on the water", "Iron man" and other songs to Zach), but he didn't do the guitar solos.
Originally in the script, Dewey had supposed to have run the teacher over before she came to school which stopped her from teaching the class for 3 weeks. After, they changed it to her falling in the shower instead.
There was a part in the original script where Freddy Jones, played by Kevin Alexander Clark, would forget his drumsticks to class and having Jack Black to say: "Would Keith Moon forget his sticks? No! He might get drunk and pass out on the floor, but he would never forget his sticks!"
After the first band rehearsal, Dewey gives the kids some musical albums to listen to at home for inspiration and influences. The albums are: "Led Zeppelin" by Led Zeppelin, "Parallel Lines" by Blondie, "Fragile" by Yes, "2112" by Rush and "Dark Side Of The Moon" by Pink Floyd.
When the class are at the tryouts for the Battle of the Bands contest, Summer and Dewey are on the stage talking to the director. In this scene, when Jack Black's character gets frustrated, he throws a chair. According to the commentary on the DVD, this wasn't part of the script and Miranda Cosgrove didn't know this was going to happen. You can see her react by jumping when the chair is thrown. This is a completely real reaction.
The Mooney Suzuki:
As Dewey heads into the Battle of The Bands contest towards the end of the film he walks through a corridor and past two musicians wearing shades, leaning against a wall. The two are members the band who provide extra instrumentation on the soundtrack.