There are lots of good grammar programs out there, but I'm including a link to just one.  Just this year, we started using Analytical Grammar, a fairly new product that offers to provide a complete education in grammar in as little as one year.  We are so happy with this grammar program.  The kids are learning, we all look forward to doing grammar together, they are getting difficult concepts through practice and good explanations, and it won't take 8 years for them to get it!  In addition to the primary product, Analytical Grammar, there is also a junior version for 4th and 5th graders as well as reinforcement exercises for between the Analytical Grammar "seasons" if you decide to spread the program over several years.