A very Clintonian definition. Give a couple million years and all these little mutations start to add up and the critters start looking very different.
Indeed they do. But you need to take two further steps before you can push the theory of evolution to the extent some people do. You first need to prove that the changes involved in micro-evolution can occur in such a sequence as to yield certain types of changes. While there's enough randomness in mutations that just about anything 'can' happen, some things don't seem very plausible. For example, how could an egg-laying species which relied upon external fertilization evolve into one that relied upon internal fertilization? It would be necessary to have a genetic mutation affect enough males and females to yield a sustainable population with such a trait, since all internally-fertilized egg-layers would have to be decendants of that population. While such transitions could conceivably happen, it seems doubtful that they would.
Even if mechanisms are shown by which the right kind of mutations could occur by some freak event, that still does not cross the second step: did things in fact happen that way. Again, conceivable but doubtful.
IMHO, the science of what some would call 'microevolution' should be tought in science courses since it can be experimentally demonstrated. It would also be proper to teach that while such mechanisms are responsible for at least some of the diversity of life on this planet, it's unclear exactly how much.
Where are the transitional forms. Where are the long chain of human anscestors who had first a little bump, then the next one had a slightly larger bump, then the next one had the beginning of a knuckle, etc etc etc.
Where are all the transitional forms?