First, a significant percentage of mainstream society adheres to creationism; the same cannot be said for alchemy or any of the others. Debunking something no one believes in is a pointless exercise; debunking someone's actual misconception may be necessary to getting that person to consider the alternative.
Second, I don't think one gets a proper respect for the power of the ToE to describe what's going on (and has gone on) in the world without looking at the inability of any other theory to do so with any reliability.
And it's not like it's entirely without precedent to teach theory "B" in part by pointing to the flaws of its predecessor, theory "A" (and how "B" solves 'em). For example, I still recall learning in astronomy class about the problems with the circular planetary orbits hypothesized by Copernicus leading Kepler to formulate his laws (and theorize that planets had elliptical orbits).
Like I said, I think the bigger problem would be Christians who also believe in evolution thinking that the debunking was unnecessary and therefore a gratuitous attack on Christianity.
In that sense, it would make sense to teach evolution in the context of 18th and 19th century conceptions of the universe as a clockwork whose laws are knowable to scientific examination. Evolution would be prefaced by a discussion of the state of the life and geological sciences previous to Darwin. This sort of chronological approach would make clear how long evolution has been central to biology, and would also illustrate how many later challenges and discoveries have strengthened the theory (DNA, plate tectonics, etc.)>
Yet this would all take away time from discussions of photosynthesis, cell structure, anatomy, frog dissections, and the other frequent topics of middle school and high school biology.