I agree with the the majority on this thread, but if the parents are going to pull them anyway then I have a few recommendations.
Teaching Textbooks for math - We use this, but I'm very involved. I always ask them if they understood the lecture before they start their arithmetic, and if things aren't clearly understood then we go over them together. We do not move on until whatever it is is mastered.. My kids work in the workbook and then type their answers into the computer for grading. We go over all missed problems together even though they've already seen them solved properly via TT. My children are not allowed to use the "Try Again" feature because I found that they weren't as careful solving the problems in their workbooks/the first time. We do no formal math just games until 3rd grade and use TT on grade level. I do not expect us to continue with TT much past elementary age though.
We also incorporate Cuisenaire rods into our math. We like Education Unboxed which is a free website filled with math videos showing all elementary concepts explained with C. rods and how to use them as manipulatives, if necessary.
My kids LOVE math and use it constantly in their everyday. We have a grocery store near our home, and they ride their bikes to do light shopping for me occasionally for fun. They love figuring out the best deal by figuring the cost per ounce, pound, etc. I've always made it a point to stop and share with my children or have them help me figure out math when I encounter it in our everyday life. I think that's invaluable.
Explode the Code for reading, handwriting, and basic spelling instruction - I love this! I add Leap Frog dvds, Happy Phonics games and beginning readers like Bob Books to it.. Great Combo.
Handwriting with Tears Cursive - Great for my oldest who is a lefty and fun for my right handed son, as well. They have beautiful cursive.
Growing With Grammar - I have my dc read their lesson to me and we do the first problem in each section together. We also do the "2 review and 1 new" rule at the beginning of our grammar time which basically means that I have them narrate the previous two lessons subjects to me and then we go on to the new lesson. We also do The Sentence Family and Grammar Land prior to GWG.
Rod and Staff for Spelling - Again my children are elementary age, so they do not do this independently.
Writing is my own thing put together using several writing curricula as a guide, so I have no recommendation(s) for you there!