this is bad...you should maybe talk to the headteacher and tell her that you have concerns and that what the teacher is telling you is not reflective of your childs personality, also ask classroom assistant and lunch time supervisor and see if they all feel the same way about your child...
it is worrying because a child can so easily get labelled as problematic and then he will have this reputation throughout his schooling, and he will always act this way as he is 'expected' to by all those around him.