Competing is the key word. I knew somebody would try to make the case you made, but that argument is invalid to me. Very few--if any--people believe theories other than a form of ID or Darwinism. Students should hear what the top scientists in the field are studying--that would be ID and Darwinism--not some garbage about aliens.
My point was that, scientifically, Last Thursdayism or Native American creationism or Islamic creationism, are just as useful as ID (or creationism). They make no predictions and have no explanatory power and hence are useless scientifically, as is any idea that references a supernatural power. If you want to argue that there is was a non-supernatural intelligence that interferred with the development of life, then fine, let's see the positive evidence of this. Until such evidence is shown that cannot be explained without reference to such an intelligence, then such intelligence will be assumed not to exist by science. Outside of science, of course, people are free to believe and schools are free to teach anything they choose.