Blame it on:
- lack of parental guidance. Never teach them good manners since
young.
- bad company. e.g friends teach vulgar language or get influenced
friend's rude behaviour.
- environment. e.g school full of gangsters, slackers, play
truants,etc. Not a conducive place to study and excel.
but I believe there are some good kids too. It's just the matter of
upbringing that makes a kid behave good/bad.