Online, interactive Grammar for High School Students - Even if it costs!

I'm looking for an online, interactive grammar program for freshman English students to review and strengthen their grasp of grammar and punctuation. Ideally, the program would be online so students can work at home, at their own pace, a unit at a time with a test module that only the teacher can unlock at an appointed time. Basically, it would be like a workbook, but interactive so students could learn and apply the concept as they go along. If it tracked student progress, that would be ideal.

Thanks.