...the one that us teachers use that goes something like,"If you promise to not believe everything your kid says about me,I promise to not believe everything he says about what happens at home."

That's very true and useful but I've been doing this for 15 years and this one I sense has more than a grain of truth to it. That's both instinct and knowing the background ,I guess. The child's grandparents are my landlords and live next door, so I do have a good idea of what life is like outside of daycare (and one of the relatives has complained about the mother to me along similar lines.... and I behaved myself and said nothing back *pats self on back* )