Rather than preface teaching the theory of evolution with a disclaimer that "this theory is a theory" it might be easier to each kids that all scientific output is theory. Gravity, electrons, etc. is all theory. A thorough grounding in the scientific method should serve to fix this "theory" complaint.
Hey, maybe that's something the ID folks maybe could learn too!
(Nah, its been tried.)
"All Theories Are Theories."
I like it. Gotta good beat, you can dance to it. :)