You hate it when people tell the truth?
Both creationism and ID have been literally put on trial (see
Edwards v. Aguillard - Wikipedia and
Kitzmiller v. Dover Area School District - Wikipedia).
This was directly from the judge's conclusion from the Dover case:
A significant aspect of the IDM is that despite Defendants' protestations to the contrary, it describes ID as a religious argument. In that vein, the writings of leading ID proponents reveal that the designer postulated by their argument is the God of Christianity. Dr. Barbara Forrest, one of Plaintiffs' expert witnesses, is the author of the book Creationism's Trojan Horse. She has thoroughly and exhaustively chronicled the history of ID in her book and other writings for her testimony in this case. Her testimony, and the exhibits which were admitted with it, provide a wealth of statements by ID leaders that reveal ID's religious, philosophical, and cultural content.
And,
Dramatic evidence of ID's religious nature and aspirations is found in what is referred to as the "Wedge Document." The Wedge Document, developed by the Discovery Institute's Center for Renewal of Science and Culture (hereinafter "CRSC"), represents from an institutional standpoint, the IDM's goals and objectives, much as writings from the Institute for Creation Research did for the earlier creation-science movement, as discussed in McLean. (11:26–28 (Forrest)); McLean, 529 F. Supp. at 1255. 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).
Kitzmiller v. Dover Area School District - Wikisource, the free online library
Now I'll grant that there could be a case made for legitimate scientific inquiry into ID, but up until now (or at least up until Dover), ID was primarily a political/religious movement with the purpose to challenge science (e.g. evolution) that directly contradicted certain people's religious views (e.g. creationism).
All of this was laid bare in the Dover trial. ID proponents need to be well aware of the history of the modern ID movement.
The judge's objection though was not in the interpretation of the evidence itself; but that it was contextually religiously Christian.
So in that regard the judge is correct. Inherent in teaching ID, eventually one is confronted with which deity is "the Creator"; And here is where teaching ID in a secular educational institution becomes a matter of freedom of religion / separation of church and state.
Yet at the same time, there's no injunction against the use of a public building for community purposes, in which an ID lecture can be presented. One CR presentation I attended was actually held in a public school on a Saturday afternoon.
"Separation of church and state" never meant to take any and all religiously contextualized discussion out of the public area. It simply meant that the government could not establish a "state church" / (or state religion as it would be interpreted today)
And all that is valid. The interpretation of "freedom of speech" does say that student lead / student initiated discussion of religious subjects is permissible in public schools (particularly where attendance is mandatory). And that staff are allowed to have individual religious discussions with students who seek that teacher for that purpose.
Schools get into sticky wickets though with religious freedom as it applies to extra curricular activities / clubs or elective courses available. This is not as big of an issue with public universities. But schools tend to exclude all activities related to religious beliefs in favor of "fairness to all" means "none are allowed". And technically, that's valid too.
Public schools can actually "mandate" educational curriculum that teaches comparative religion, religion as it applies to society as part of a history or social studies class, religious books as literature etc. But they can not present a belief system as "religious instruction".
Now that all being said; public schools that are in areas that predominate populations of specific religions run into this conflict frequently and since school boards being elected by the populous of the local community - this is why you have Muslim dress codes in public high schools in Minnesota and Torah classes in public schools in NYC. (Both of which still get governmental funding.)
Now where do you draw the line between constitutional right and what is actually "religious instruction" and still maintain your public school status as opposed to crossing over into the sector of private education?
In the US there is a broad variety of educational options available. There's public school, private school and homeschool. We are the only nation in the world that has that extent of flexibility. In most of the rest of the world education is far more stringently regulated than it is here. In half of Europe, home schooling isn't even legal.
So yes, in general terms - I do agree with the system as it is. And ID will always be relegated to the realm of private / independent instruction. Yet, just because that's the case; does not negate a concepts validity as truth.
Truth, regardless of what it is in relation to - is always relegated to the margins. Want further evidence; start investigating subjects like the German side of WWII, the Palestinian / Arab side of the Middle-Eastern conflict, the "official narrative" of 9/11 (does it even match the footage you are watching of the event)?
In the current age of the information superhighway - the Internet has been the leveler of many things!