Please add Math and Science placement tests

It would be cool if Khan Academy could make placement test for math and science. Since it would be online, the test would be more interactive and could also be an adaptive test, which would be unique. Final, Midterm, and Quarterly exams for each course (like Biology, Geometry, Algebra, US History) would also be really beneficial.

Also, Khan Academy should further develop the English section by making videos about vocab and how to write essays.

Thanks!