The SAT subject tests for high school courses and the Advanced Placement exams for college courses.
I think this helps for older students, but I'm looking for something less than AP or SAT level that demonstrates pre-AP level science that demonstrates readiness for AP.
That's the level SAT subject tests are at. A high school student taking AP biology, chemistry or physics has usually taken a prior course in these subjects, taught at the level of the SAT subject test in the subject.
It may not make sense for a pre-high-school student to actually take SAT subject tests (unlike the SAT reasoning test, which is used by talent searches), but since books with practice tests by the College Board and tutoring companies are inexpensively available, the SAT subject tests can be used informally to assess readiness.
