Is this disclaimer unconstitutional?
Naughty again. LOL. Let's see if your naughtiness is caught by your interlocuter. :)
In and of itself, no. When you insist on posting it in a high school science book, along with recommending a barely warmed over creationist text which a local church paid for, and than lying in court about it---yes, it is unconstitutional, it violates the 1st and 14th amendments. And intention does matter here: If the intention was to make an honest, if mistaken attempt to improve science teaching, it is merely flagrant incompetence. If, as turned out to be the case as a matter of judicial record, your intention was to divert students into reading an overtly creationist text, and you made that painfully obvious by committing perjury to hide the fact, then you are trying to divert public resources in support of a specific religeous creed. You violated the constitution, and committed perjury about it. It may well produce a ride in jail for the miscreants, intention is that important.