Freedom Homeschooling - Free Homeschool Math Curriculum Khan Academy (K to 12th) Khan Academy uses video-based instruction. Online practice problems, quizzes, and tests are included. Courses covered are K through 8th grade math, Pre-algebra, Algebra 1 & 2, Geometry, Trigonometry Pre-calculus, Calculus, Multivariable Calculus, Differential Equations, and Statistics. Some AP courses are also offered.