There's actually some kind of debate going on about adding a "multiethnic" box to school applications, I think particularly in California. Many people don't want it because of the fact that everyone of biracial or multiethnic background will be thrown in together. In my opinion, that doesn't have to be the case, just like checking "other" doesn't have to keep you raceless. For the record, I didn't check "other"--for schools that had where you could further self-identify, such as the U of Michigan app, I did so but checked my "predominant" race. Other than that, I made sure I included diversity statements and also mentioned my multiethnic background in my main personal statement. But I think schools should have that multiethnic box with a line beside it where you can fill in whatever you want to include or the option of including an additional statement regarding your background.