If it were me and it was effecting my child or making them no longer wanting to go to prechool i would definately say something. Even though they are young, it is a form of bullying. There was something in DS's prechool newsletter this week that they are addressing bullying so its something they are aware happens at that age. Im sure the kids wont get in to trouble.. it will just give the carers a bit of inside info on something they need to look out for.