It was taught as a fact, and if someone objected the Founders would have had the objector take it up with their school board, not a court.
I'm using "creationism" as the example since it was the case at the time. "Creationism" and ID are not synonymous.
Would either of you object to teaching that life developed without a designer?
Actually, the major reason behind the public school movement in the first place was because of concern regarding religious teachings being provided in the private institutions that made up the school system of the time, beginning in 1818, when Boston became the first American city to establish a complete government-financed school system, and continuing up through the 1830s and 40s with Horace Mann and the rise of the government school system.
Before that time there were no tax-funded schools, so of course the founders would have no jurisdiction over those school boards.