What about Beestar.org? It's a semester-long progressive program. It doesn't teach, per se, but it has two 10-question quizzes that get harder as the semester goes on, and gives you ideas for teaching. The basic math is free; there are other subjects that are $20-$30 for the semester.
Scores are tracked, and kids can earn places on the "honor roll" for accuracy and speed.
Watch grade levels, though; last year in K, ds-now-6 had no trouble whatsoever with grade 1 and grade 1 GT. I just signed him up for Grade 3 for this spring, but looking at the samples I probably should have signed him up for Grade 4 for a bit more thinking.
