Leaving the evolution VS creationism debate aside, the fact is that the sole argument for ID is "it's too complex, therefore it must have been designed by a supernatural intelligent being", which runs counter to methodological naturalism, which is one of the most basic pillars of the scientific method.
In other words, even if you ignore the facts that...
- All the most common examples of ID (such as the spermatozoid's flagellum and the human eye) have been falsified.
- 99.9998% of all scientists who got their degree and work in a field related to evolution (i.e. biologists, biochemists, and paleontologists) accept the theory of evolution.
- The almost totality of ID proponents are Christian fundies, and those who aren't are usually making lots of money by selling various books and other merchandise about creationism and ID.
- ID doesn't actually explain anything, all their arguments either attempt to falsify evolution (as opposed to attempting to support ID), or are based on the "argument from ignorance" logical fallacy.
...intelligent design can't be called science, even by the vaguest meaning of the term. It's not "bad science" or "science based on shaky grounds"; by its very definition, ID isn't science at ALL, and has no place in a science classroom.