This might sound callous, but the quicker and more perfunctory you make handover the better. The longer you hang on with the kisses and hugs, the worse it gets.
Really, unless you actually need to see the teacher for some reason, try to make it a quick "Bye, love you , see you at hometime!" and go. If they are crying when you leave, it won't last for long, we will divert their attention.
There are some parents who make a huge show of how much they love their children (E.g. kiss mummy, kiss daddy, kiss baby brother/sister, huge bear hugs, "love you sooooo much",hang their coat up for them, put their lunch box on the trolley for them, walk them to the classroom, big hugs and kisses again, etc,etc) - it is almost a competition! - and theirs will be the unsettled, " I want my mummy" children. 
NB; I am absolutely NOT saying that I think this is how you are, OP!
Just generally pointing out that there are some people who really don't help the situation, with their "nobody-loves-their-children-more-than-me" attitude.
I like the secret stretchy rubber band idea catkind