This seems to have the same problem as teaching evolution in high school biology classes: you can pass a test on something and not believe a word of it. Cracking an information cocoon can be damn hard; just consider how unusual religious conversions are, or how rarely people change their minds on such subjects as UFOs, conspiracy theories, cryonics, or any other subject that attracts cranks.

Also, why should employers care about a person's climate change test score?

Finally, why privilege knowledge about climate change, or all things, by using it for gatekeeping, instead of any of the many non-controversial subjects normally taught in high schools, for which SAT II subject tests already exist?