Why are people like this nowadays?

How come just because i don't have an iphone or the best 200$ shoes i'm not important to anyone at school?

Who cares

Who cares, don't worry about others, worry about yourself.

Partially, because that's what you want to believe. And partially because those people really do not know what is valuable in the world. Take away their iPhones and $200 shoes and they wouldn't know what to do with themselves.
Bottom line… You know what is and is not important in life… You can either educate the rest or simply go on with your life knowing that you are more important than their "stuff" and them.