Git! (1965)

Deke, a runaway orphan from a boy's home, is arrested when he prevents Art Finney, a trainer for a wealthy California dog breeder, Andrew Garrett, from shooting "Rock", a renegade English setter and alleged animal killer. Garrett has Deke remanded to his custody and gives him a job assisting the (highly) resentful Finney and also working with "Rock", whom Deke insists has the makings of a fine hunting dog. The trainer and owner/breeder don't think so, but they accept the word and non-experience of a 17-year-old orphan?