If you look at the definition I posted for "theory" you will note that it begins with:
a well-substantiated explanation of some aspect of the natural world; an organized system of accepted knowledge that applies in a variety of circumstances to explain a specific set of phenomena.In science, this means that the theory has been tested against the known facts, and that it has passed those tests. It also implies that the theory has produced predictions, and that those predictions have been verified. This is the explanation that currently best explains the data.
This does not mean the theory is correct, or that is is proved or that it is fact, but that it has passed the tests I mentioned. This follows the scientific method.
What the proponents of ID are asking scientists to do is accept unverified beliefs as being equivalent to well-substantiated scientific theory. In a science class that is not an acceptable alternative. There is no "teach the controversy" or "teach both theories" as ID has not yet been able to establish itself as a part of science, nor does it follow the methods of science.
Would you care to guess the percentage of their annual budget that the Discovery Institute spends on public relations vs. actually doing science?
Would that really be a guess?