As part of their homeschooling, my daughters attended classes held by Don Cohen, better know in the Champaign-Urbana area, as The Mathman. He and Jerry Glynn have been offering algebra, calculus and advanced math classes for over 31 years. They truly know how to make mathematics fun and interesting to both children and adults.
This graph is from daughter #2's workbook:
What I really liked about the program was they allow children to develop their own problem solving skills in math; they show how one can solve math problems many different ways and still arrive at the correct answer. They also introduce highly complex math problems at early ages and show the relationships of easier math to more complex problems. And all of this is done in an exciting, fun environment.
Both daughters did extremely well in all subsequent math courses in high school and college and received high scores in the math portions of college entrance exams.