Why we shouldn't "Teach the problem"
First, even if there were dissent, (which I remind you there's not), no one is denying that an overwhelming majority of biologists strongly endorse evolution, nor, in fact, is anyone in ID denying that organisms do evolve by natural selection. Suppose they were right that neo-Darwinism can't account for some traits. It still accounts for the vast majority of traits; it still explains homolgy and biogeography and many curious facts of anatomy and physiology; it is still strongly confirmed by a huge body of evidence.
So, rather than "Why not teach the 'problems' and 'alternatives'?" I think the question we should be asking is, "Until ID is also confirmed by a huge body of evidence, why teach it?"
Here's the analogy I have in mind: High school physics, if it even gets to relativity, doesn't address the fact that there are serious problems for the theory (and now we're talking about real problems, unlike when ID people talk about evolution). General relativity is not compatible with quantum mechanics in some cases, though both are very highly confirmed. Thus, physicists have been searching for a way to unify these theories for decades - so far, to my limited knowledge, with little success. Would we think that high-school physics teachers should start specualting about string theory? I suggest that this would be absurd. And string theory isn't even a wedge for creationism!
As a general principle, before you can effectively criticize a theory, you must first learn what the theory is. ID proponents frequently engage in behaviors which suggest that they do not believe this; therefore it is perhaps not surprising that they would argue in favor of teaching kids how to attack evolution before teaching them how it got to be so widely accepted in the first place.
Since that is precisely the argument being advanced by some creationists, this is a nice summary of what the real issues are.