My math-challenged daughter couldn't wait until I cracked open the Middle School Math Advantage collection. She was having a bit of difficulty with her high school math courses, and figured this would help her catch up. Pre-algebra ranged from place value to fractions. Algebra covers real numbers to inequalities. Geometry covers parallel lines to pyramids.
Measurement covers everything from metric units to measuring angles.
Statistics gives a good overview of bar graphs and random samples and everything in between. Probability covers independent events to permutations. Each course lets students choose from dozens of math topics and hundreds of examples. After you've learned how to solve problems, your student gets tons of opportunities to practice. Best of all, there are word problems that put to practical use the theories they've mastered.