The Art of Problem Solving mathematics curriculum is specifically designed for outstanding math students in grades 6-12, and presents a much broader and deeper exploration of challenging mathematics than a typical math curriculum. The Art of Problem Solving texts have been used by tens of thousands of high-performing students, including many winners of major national contests such as MATHCOUNTS and the AMC.
AoPS was started by Richard Rusczyk, who participated in national math competitions in high school and went to Princeton. AoPS wrote a set of math texts for Algebra to Calculus, has online, interactive classes.
Beast Academy is the new elementary school curriculum from Art of Problem Solving! When complete, Beast Academy will provide a full, rigorous, and entertaining curriculum for aspiring math beasts in grades 2-5. The series consists of 8 books per grade, which consist of four sets of two books: a Guide book presenting the lessons and a Practice book providing exercises and problems to reinforce the lessons.
Life of Fred is a fun series of math textbooks that start with elementary math and go to calculus, statistics and linear algebra. The books tell the story of Fred Gauss, a five year old professor of mathematics at Kittens University. Through the adventures of Fred, students learn math. Some kids just like to read the story and skip the problems. Eventually, they go back and work on the problems. Periodically, the books have review quizzes called bridge tests.