Three operas by Benjamin Britten

Benjamin Britten wrote three operas to be sung by children and adult singers. 

"Noye's Fludde" (http://www.brittenpears.org/page.php?pageid=476

The Chester Miracle Play set to music by Benjamin Britten. Op. 59 (1958).
The text is from ‘English Miracle Plays, Moralities and Interludes’ 18 June 1958 Orford Church, Aldeburgh Festival .
Noye’s Fludde, completed in December 1957 and first performed during the 1958 Aldeburgh Festival, is his most extended and elaborate work for children. In common with Saint Nicolas and The Little Sweep, the work is written in such as way as to combine professional and amateur performers, the music often tailored to take account of the abilities of less accomplished players but without any sense of compromise or writing down. Most of the main vocal parts are written for children (the exceptions being Noye himself, Noye’s wife and the Voice of God) and the orchestral forces comprise strings, recorders, bugles, handbells and a large assortment of percussion including such home-made instruments as sandpaper blocks and slung mugs. The congregation also gets the opportunity to participate in three hymn-settings. 

"The Little Sweep" + "Let´s make an opera". (http://www.brittenpears.org/page.php?pageid=472

An entertainment for young people. Op. 45 (1949). Libretto by Eric Crozier.
 "The Little Sweep" can be performed with or without the accompanying "Let’s Make An Opera". Alternative versions of the play have been and can be written.  First performance: 14 June 1949 Jubilee Hall, Aldeburgh.

 Video: http://youtu.be/A_gQcHYcBJQ 

Two of the major preoccupations informing Britten’s life and work, opera and music for children, come together in this ‘Entertainment for Young People’, the first part of which, Let’s Make An Opera, consists of a play in which we see a group of children and adults write and rehearse an opera; the second part consisting of a performance of the finished opera itself. 
As such, the work can almost be seen as Britten’s operatic counterpart to The Young Persons Guide to the Orchestra. 

Yet despite the light-hearted approach, "The Little Sweep" is also a morality tale in which Sam the sweep boy is sold into service and bullied by his elders in a manner reminiscent of "Peter Grimes". Thus the work embodies a rounded and involving theatrical experience, introducing young audiences to the conventions of opera by means of a simple yet affecting story with which they can sympathise and identify. That Britten undoubtedly succeeded in his aim is demonstrated by the work’s universal appeal and popularity.