I think...
String theory is still a theory that scientists will try hard to prove or disprove.
At its fundamentals, it is a theory based on the extrapolation of current thought, logic and scientific thinking.
ID on the other hand, is a bunch of people who can't explain why the world works the way it does and say that someone must have therefore ordained it thus. This is not based on any logic, previous observations or any form of intelligent thinking. And accepting ID for what it's worth implies that had this theory caught on back in the 1600s, we would still think that air and earth were elements. After all, we don't understand it, so someone created it like so, and so it must be.
Though I am an atheist, I understand why some people might want to push for ID to be taught in school. However, it doesn't mean you are right. How would this group of people like it if we made them learn islam by saying that is an alternative ID?