Even worse imagine history taught that way. Whoops that's pretty much how they do teach history and (coincidentally?) that doesn't work too well either.
Would a philosophy class really be good for high school students? Broadly speaking, I mean, not those 1 out of 100 students who are reading Sartre or Nietzsche (or even Dostoyevsky or Kafka) on their own, already, anyway.
A survey course, I mean, a 101-type of course, like you would see at a University. My feeling is that a course in introductory logic is the #1 most useful course that's missing in high school right now.
And again, there are going to be a few students for whom this would be redundant, but something like 99/100 students do not understand the machinery of thinking. If there's one thing my university education taught me, it's the machinery of thinking, carefully and rigorously. Most people never learn this, and I feel like this then precludes any understanding of anything advanced and even slightly abstract--and that includes both philosophy and (of course!) mathematics.
This is barely touched in standard geometry text books. 2-column proofs and all that.
But most people don't notice it, and it deserves far more treatment. Many of the smartest people I know attended special gifted programs in K-12 that did teach formal logic and informal critical thinking skills.
(correlation != causation, though)
I can't speak to anyone else's experience, but I found being exposed to Philosophy while still in high school to be quite meaningful, and went on to dual-major in it while in college.
That being said I also remember being one of the few students who felt the course interesting and worthwhile. Most of the other students saw it as a waste of time and focused mainly on how to get a good enough grade to not affect their overall average while doing the least amount of work possible.