When facing a proposal such as Intelligent Design, the court must look at the intent of the law, not just the words on the face. This is clear from the following:
"The Supreme Court has consistently held not only that legislative history can and must be considered in ascertaining legislative purpose under Lemon, but also that statements by a measure's sponsors and chief proponents are strong indicia of such purpose." McCreary County v. ACLU, 125 S. Ct. 2722, 2734 (2005).
What does this mean for Intelligent Design? It means we have to look at (pardon the pun) the evolution of ID over the years. We started with states passing (or attempting to pass) anti-evolution statutes, which were struck down in Epperson v. Arkansas, 393 U.S. 97 (1968). From there, states tried to enact equal treatment statutes, which failed in part because the people proposing such statutes made errors in drafting (for example, statutes that required evolutionary texts be labeled as "theory" while biblical/Genesis texts did not). The next step was to change the cover of Creationism by giving it a new name. Instead of being "Creationism," it became "Creation-science" or "Scientific Creationism." These concepts were forwarded often forwarded by fundamentalists or groups with fundamentalist backing. The concept itself arose specifically from Genesis, which, combined with the stated intent of many of the original backers of CS (Arkansas' proposed Creation science Act, where in deposition, promoter Paul Ellwanger, admitted that the language of the act had been revised to insert "creation science" in place of creationism because creationism was, in Ellwanger's impression, too religious a term [from depositions for McClean v. Arkansas Board of Education, 529 F. Supp. 1255]). This led to a change in terminology from Creation-Science to the current term "Intelligent Design," which purports to include potential "designers" outside the book of Genesis. After Edwards v. Aguillard struck down Creation Science nationally (it's a Supreme Court case), Intelligent Design came to the forefront. However, the concept of Intelligent Design is not a new one. Indeed it stems from St. Thomas Aquinas, who proposed ID as a purposeful arrangement of parts from an intelligent designer, which Kitzmiller expert witness Dr. John Haught stated "everyone knows it to be God." In Kitzmiller, even the defense witnesses conceded that many of the proponents of ID believe the designer to be God, which indicates the intent of the ID movement.
Even more damaging to the ID program are the "Wedge Documents." From Kitzmiller:
The Wedge Document states in its "Five Year Strategic Plan Summary" that the IDM's goal is to replace science as currently practiced with "theistic and Christian science." (P-140 at 6). As posited in the Wedge Document, the IDM's "Governing Goals" are to "defeat scientific materialism and its destructive moral, cultural, and political legacies" and "to replace materialistic explanations with the theistic understanding that nature and human beings are created by God."Kitzmiller v. Allegheny County, 400 F. Supp. 707, 720
Additionally in Kitzmiller, one of the school board members repeatedly made statements at meetings expressing a desire to reintegrate religion in the public schools. Combined with the subsequent passage of the ID program and the conclusion that ID is a religious instruction program in disguise, you have a problem, and a violation of the establishment clause as a government entity (the school board) is attempting to establish religion (through ID).
(This is a VERY quick and abridged overview of Kitzmiller. I highly recommend reading the entire case to anyone who is interested in how the ID program failed to pass judicial muster.)
So the problem remains how could one integrate ID into public schools? The problem is not what the proposed ID program might be; rather the problem is from where ID came. The purpose of Intelligent Design is not to propose a different option to students; it's to propose a Biblical/Genesis option to students. It completely overlooks other possibilities, such as Romulus and Remus, or the Korean Mother Bear, or whatever other hypotheses are out there. From my estimation, it would be impossible to create a working ID program for public education. However, a world religions class, or a creation-theory class that encompassed several hypotheses and granted equal time for each to the student could possibly work, if it was facially neutral in proposal and offered no proselytizing whatsoever. That is for a different post, though.