I' am a teacher so I know what the OP is getting at. Like others have said we sometimes accept that some kids are just a lost cause and there is nothing we can do. You can only tell a kid so many times to not come into school with trainers instead of shoes or to wear the correct trousers etc. Unfortunately we have no real power to discipline them, the head teacher can try to get them excluded but it usually ends in an appeal and the kid in question gets let back into school.
The rest are usually decent kids, if we tell you off its because we want to keep the same standards. Its very unfair I know but in a couple of years time you will probably have moved onto further education or got a decent job. Most of the kids who you see seriously disregarding authority at school level usually end up in more trouble down the line, perhaps with the law or they have no qualifications etc and are unemployed. We obviously try to get these kids to sort their lives out but it can be very hard if they and their families are unwilling to cooperate, its also not fair to focus all our attention on them when there are other kids who need to learn etc.
The rest are usually decent kids, if we tell you off its because we want to keep the same standards. Its very unfair I know but in a couple of years time you will probably have moved onto further education or got a decent job. Most of the kids who you see seriously disregarding authority at school level usually end up in more trouble down the line, perhaps with the law or they have no qualifications etc and are unemployed. We obviously try to get these kids to sort their lives out but it can be very hard if they and their families are unwilling to cooperate, its also not fair to focus all our attention on them when there are other kids who need to learn etc.