well, heres one trick. tell the boys who do this that youre a girl and you want to be treated like a girl, and give them specifics or they might take the wrong way, in a lot of different ways. thats the best "trick".
While magic cannot change this, many other factors can. Talk to them and let people know how you wish to be treated, communication is a magic all in itself. Another way would be wearing make-up or dressing in drag.