1) "Kes" (1969) is about a boy growing up in a working class mining community in Yorkshire, England. If you've seen the movie "Billy Elliot,"this is a rougher, bleaker and more authentic portrait of a society in transition ("Billy Elliot" was heavily influenced by this film). The British Film Institute considers "Kes" one of the ten greatest British films of all time. Due, perhaps, to heavy regional accents, this film is virtually unknown in the USA - you will need to order this one overseas, and have the ability to play DVD's from other regions. Or, I can lend you my copy. If you know me. Directed by Ken Loach.
2) "Over the Edge" (1979) is, once again, about a society in transition. This time, it's smack in the middle of modern USA suburbia, where a planned community didn't plan for the teens in its midst, resulting, ultimately, in chaos. It's about teens as a social footnote, and it's also a interesting portrait of 1970's teenage angst. There's also a great contemporary soundtrack of the time, and a pretty effective cast of alienated kids, including Matt Dillon in his first role. Directed by Jonathan Kaplan.
3) "Pixote" (1981) is about the life of a street kid in Sao Paulo, Brazil. It's probably the most intense film of its kind - and even today, is a difficult film to take, if you're squeamish about such things. There are millions of desperate kids living hopeless lives on streets around the world. Unlike some other films on the same subject, this doesn't soft pedal the huge odds these kids face. Directed by Hector Babanco.
4) "Lord of the Flies" (1963) is a faithful adaption of the classic book by William Golding (as opposed to the bizarre 1990 American version) about a group of English schoolboys who descent in savagery while stranded on an island without adult supervision. Though this film sometimes seems stiffly acted (the kids were cast mostly from British expatriates in America), it's a fascinating bit of independent filmmaking by Peter Brook. I had to watch this film numerous times in junior high and high school. so it's become ingrained...