Getting attention from kids

    I am a kindergarten teacher (children from 3 to 5) who's
    been facing troubles to get them attention. I feel they
    don't give me any respect, since they start chatting as
    soon as I come to the class. Some of them turn back and
    just don't care about the class. I am very disappointed!
    When I taught adults and teens a few years ago it was
    totally different! They loved my classes! Now, with the
    youngers I am considering to give up! Could anyone
    advise me with some tips to make the children pay
    attention and enjoy the classes?