You may want to check out Thinkwell Homeschool. Thinkwell offers courses in middle school math, a variety of high school subjects, various AP courses--the least expensive course for AP I've found that include full problem sets--and college level courses.
I've used Thinkwell in the past for PreCalculus and this year for AP Chemistry.
The video lectures are clear and hold a kid's interest. The problem sets are immediately scored. Videos and problem sets can be watched and worked as many times as necessary. Test and exams can be taken only once. The courses appear incredibly comprehensive--it took my extremely math oriented son a full year to work through PreCalculus. He went on to ace the first three Calc courses at our regional four year college, so Thinkwell prepared him well. This kid went straight from Geometry to PreCalc and Thinkwell's PreCalc included all the Algebra II and Trig he needed.
Subscriptions are valid for one year. That year starts from the day you register the course, not the day you purchase it, so you can make advance purchases if you like. I bought two AP Chemistry subscriptions so that my sons could take the exams separately, but it would be possible to combine kids in one course if separate exams were not a priority for you. Printed course notes and the lectures on DVDs are available for extra cost.
If you use my email, firstname.lastname@example.org, in the referral box when you order, you will get a $10 discount. I, in turn, will get an Amazon $25 gift card. Win-win! I hope you enjoy these courses as much as my kids have.