Kids Rock

There are some messages that can be expressed only in song. Then there are the messages that can be expressed only by the hypnotic sound of a children's chorus, which makes them ideal for singing your refrain. The results may range from legendary to awful, but one thing's for sure: There's nothing like borrowing the innocence of children to let people know how important your message is.

Not surprisingly, many of the songs tend to be about children or teens.

Related to Three Chords and the Truth. NOT to be confused with Little Boy Blue Note, in which the children themselves are the credited performers, or Kidz Bop, an example of such.

Anime

 * Very common in Super Robot theme songs, in this case to establish how the world's children are relying on the robot to protect them.
 * A notable example is (of course) Neon Genesis Evangelion... where the effect is batshit terrifying.
 * A chorus of children is used in most versions of the Title Theme Tune for The Mysterious Cities of Gold, modeled on the original French version, like the English or Spanish ones.
 * It happens in theme songs to other anime as well. One example is Galaxy Express 999.

Films -- Animation

 * Wilco's "Just a Kid", justified in that it was made for the SpongeBob SquarePants movie.

Films -- Live Action

 * What about that scene in ~Monty Python's The Meaning of Life~ where the kids are pouring out of cupboards and dancing in the streets singing about the importance of every sperm?

Music

 * Used to awesome effect in "I, the Swan" by the Sound of Animals Fighting.
 * "You Can't Always Get What You Want" by The Rolling Stones with the London Bach Choir (children's choir).
 * Pink Floyd's "Another Brick in The Wall, Part II".
 * P.O.D's "Youth of the Nation".
 * XTC's song "Dear God" starts with a lone kid who sings the first stanza and the very last line.
 * Alice Cooper's "School's Out".
 * Jay Z's "Hard Knock Life (Ghetto Anthem)".
 * The Red Hot Chili Peppers' "Aeroplane", featuring Flea's own daughter.
 * S Club 7's "Have You Ever?".
 * Justice's "[D.A.N.C.E.]".
 * Daz Sampson's "Teenage Life", the abysmal UK entry to Eurovision 2006.* "Insanity" by Oingo Boingo.
 * "The Most Unwanted Song" by Komar and Melamid.
 * HEY, EVERYBODY! IT'S RAMADAN!
 * "Excerpt from a Teenage Opera" by Keith West.
 * "Grandad" by Clive Dunn.
 * "Grandma We Love You" by St. Winifred's School Choir.
 * Scala & Kolacny Brothers' whole schtick is covering pop and rock songs with a piano and a girls' choir. Said covers include Rammstein's "Engel", Marilyn Manson's "The Beautiful People", Die Toten Hosen's "Hier Kommt Alex" and that classic by The Divinyls, "I Touch Myself".
 * Marilyn Manson's "mOBSCENE". It's actually got a touch of irony to it: The line the kids repeat is "Be obscene and not heard," which is a shortened Oscar Wilde quote, "Little boys should be obscene and not heard", itself an inversion of the old admonition, "Little boys (or children) should be seen and not heard".
 * "Where Is The Love?" by Black Eyed Peas.
 * That's Justin Timberlake.
 * Gorillaz's "Dirty Harry", featuring the children's choir San Fernandez Youth Chorus. 2D states that he was partially influenced by Sesame Street for the song.
 * Only the "clavinet keyboard rhythms" were influenced by Sesame Street.
 * Kanye West's "We Don't Care".
 * French singer Francis Cabrel's "Il faudra leur dire" (not that surprising given that it was a cover of a song by a children choir).
 * "Never Forget" by Take That had a choir at the beginning and end of the version released as a single.
 * "Happy Xmas (War Is Over)" by John Lennon.
 * "We Are the World"
 * Every song on Jesse Camp's album Jesse & The 8th Street Kids.
 * "I Wish It Could Be Christmas Every Day" by Wizzard.
 * The Carpenters' "Sing" is a particularly grating example, since it's a Cover Version of a Sesame Street song.
 * Just when you think "The Christmas Shoes" couldn't possibly get any Narm-ier, it has to break out the little kids (as if we couldn't imagine the poor little urchin chatting about his dead mom already).
 * "Toy Soldiers" by Martika (and later sampled by Eminem). Martika's version could also contain a "Shout-Out" to Kids Incorporated. Martika was a former cast member, and some of the background singers for this song included former co-star Stacy Ferguson (Fergie), along with later cast members Devyn Puett and (Jennifer) Love Hewitt.
 * "Intervention" by Arcade Fire.
 * "Who Wants to Live Forever?" by Queen.
 * "Who We Are" by Machine Head opens like this. It's notable in that it's actually NOT a source of Narm.
 * "Stars" by Roxette. Even more noticeable there because the song is a very fast-paced dance-pop number in the verses, suddenly turning almost melancholic in the chorus.
 * "We Fall, We Fall" by Dead Celebrity Status.
 * Done several times by Anti-Flag on the Bright Lights of America album. Notably "You'll Get Yours".
 * "Stardog Champion" by Mother Love Bone.
 * "Wünsch dir Was?" by Die Toten Hosen, the Kauf MICH! version.
 * Alabama did this twice. First in 1990 with "Pass It On Down", then again in 1994 with "Angels Among Us".
 * "Ain't Nothin' Like", a track from Brad Paisley's Mud on the Tires album, probably takes the cake for the shrillest kids' chorus ever.
 * "Last Dollar (Fly Away)" by Tim McGraw also has a mildly annoying children's chorus.
 * The Decemberists' song "The Hazards of Love 3 (Revenge!)" has children singing the entirety of the song. It sounds like a nice idea, until you read the lyrics, now imagine the song with nothing but a harpsichord and off-key violin as the backing track.
 * "Move Along" by the All-American Rejects.
 * Talk Talk's "Happiness is Easy".
 * They also recorded a choir for a song on Spirit of Eden, but apparently removed it at the last minute.
 * "Beat Kids" by Cage
 * "Young" by Hollywood Undead.
 * A children's choir was used on several songs Morrissey's 2006 album Ringleader of the Tormentors: "The Youngest Was the Most Loved", "The Father Who Must Be Killed" and "At Last I Am Born".
 * "Unbound (The Wild Ride)" by Avenged Sevenfold (later bridge).
 * Not rock, but still using this trope: Juan Luis Guerra's "Ojalá que llueva café" has a chorus of kids singing the refrain in the last third of the song.
 * Doctor Steel, "Smokey's Theme".
 * The chorus to Faith No More's "Be Aggressive", a song at least superficially about fellatio, has children doing a cheerleader chant of the title.
 * Featured near the end of Dio's "Rock 'n' Roll Children".
 * Yellowcard's "Paper Walls".
 * Ray Stevens' "Everything Is Beautiful" opens with a children's chorus of "Jesus Loves the Little Children".
 * "New Generation", by the Scorpions, on the last chorus.
 * Also, "Moment of Glory" and "We Don't Own the World" (kind of, because the latter one features a regular adult chorus too).
 * "*Fin" by Anberlin
 * Yo La Tengo's Nuclear War EP consists of multiple covers of the Sun Ra song of the same name, some of which include a group of children singing backup. The effect is simultaneous funny (because it involves kids gleefully shouting "It's a motherfucker!") and a little disturbing (because, well, it involves kids singing about the threat of nuclear war).
 * Generation Fade by Xavier Rudd.
 * Used cheaply and shamelessly often by 30 Seconds to Mars.
 * The Cramps' "People Ain't No Good."
 * OneRepublic's "Made for You."
 * Pat Benatar's "We Belong" has a children's chorus at the end.
 * Quite a few songs on Tori Amos' album Night of Hunters.
 * Tina Turner's "We Don't Need Another Hero" (from the Mad Max Beyond Thunderdome soundtrack). Moreover, the choir is even part of the song's lyrics ("All the children say..")
 * Nightwish's album "Imaginaerium" uses a children choir in several songs
 * Suede's "We Are The Pigs" ends with a group of children recruited from a theater group repeating the last lines of the song - since said lines are "we will watch them burn" and the children are backed only by the faint sounds of a hissing fire, there's a fairly eerie Ironic Nursery Rhyme effect going on.

Web Animation

 * In Gomu's version of Okkusenman, the theme of Dr. Wily's level in Mega Man 2, the voices of children chanting "Okkusenman!" (110 Million in Japanese) helps to underscore the song's theme of childhood nostalgia.