I watched this film way back when it came out in Japan (I could hardly understand the language) and then later on DVD with subtitles. I really loved it!! (but then, I love movies with senseless violence!). The sequel was pretty much more of the same and far too long, but it's worth watching the first one.
I remember there were many discussions on how the film was a comment on modern Japanese society, despite being somewhat cartoonish. My Japanese friend said it was a massive hit in Japan, and said that, although no-one shot anyone at his school with an uzi, he had heard of isolated instances of relatively extreme, out-of-place violence: particularly cases of teachers punish students and causing injury or death (examples I was given was a teacher forcing a student to hold the blade of a pair of scissors and slamming them agains the desk so the opposite blade cut them, and a teacher slamming a metal gate against a student's head).
I don't know if anyone in Japan can verify that these sort of things happen / happened, or whether it's an urban myth, but in Battle Royale, the scenario is that school kids have become uncontrollable by teachers, to the point of violence; so the solution is to scare or punish them in to obedience by forcing them to kill each other. Perhaps this film illustrates Japanese society's fear that it's citizens are becoming less inclined to confirm to past standards. Perhaps they worry about what society will become if people don't uphold high moral and work standards.
I know that in Australia, school is not the place I remember: There is far more bullying and harrasment, cases of violence between students. I'm sure there are more and more cases of attacks by students on staff;- not to mention the large number of students who are not even in school.
Need I mention the apparent state of affairs in American schools? I guess they didn't release this film in the states because it would be too disturbing. Perhaps they didn't want to give kids any new ideas..
(this ramble is purely my own observations and opinions, and I don't mean to offend anyone's nationality)
Kappa, you should check out 'Suicide Club' - another ultra-gory Japanese film with chilling social parallels.