"Diffidence or shyness," a phrase spoken by Richard Griffiths' character, is from the song "The Sun Whose Rays" from Gilbert and Sullivan's "The Mikado," of which this is the first film version with all the music.
One of the scenes which the boys act out in front of Hector in the classroom is the end to 'Now Voyager' (with Timms and Lockwood playing Bette Davis and Paul Henreid).