It's a non-consumable book, meaning that you don't write in it and it can be used over and over again. It even shows parents what to say in each lesson and how to teach it. If you have a used homeschool book store in your area, they are likely to have at least a few copies of it. Once you use it for all of your children, you can sell it to someone else.
For math, we have found math-u-see to be an excellent curriculum. We bought it used at a homeschool book sale and although we bought the older style, the website offers updated student workbooks to go along with the older teacher's books. This is a good way to get it for a lot less, as long as you can find the teacher's manual and videos, since the company no longer offers these. The student workbooks offered through the company are fairly inexpensive. The biggest cost with this program are the manipulatives (blocks), which I would definitely recommend as necessary. They help young children begin to see math and numbers in a different, practical way than most of us learned. (You may find it worth the time to look at homeschool book sales and such to find them used for a fraction of the cost.) I've barely ever used the videos and when I have, it's mostly been for me to learn the math-u-see creator's way of teaching a particular concept. Like the reading book recommended above, this program stimulates a completely new way of thinking. The creator, Steve Demme, points out that because of the way we pronounce some of our numbers in the English language (especially the "teens"), American students have more difficulty with math than children from languages that say certain numbers differently. He explains this better in the video and shows how to display and pronounce numbers in a new way to overcome this problem.
Overall, this method has proved to excel our children to a degree that I cannot take credit for. It's worth the investment, especially if you can find it used, which is not that difficult in today's world. You can get a free demo, either online or via mail, by clicking the following link:
For those of us who include training up our children in the Lord's teaching as one of our main reasons for homeschooling, I would like to recommend our favorite writing program. "A Reason for Handwriting" series uses Scripture for handwriting practice, similar to the way children learned to read in the 1800's. Book K is the first book and instead of using scripture, it simply introduces children to letters and words that begin with that letter. I actually skipped this book since this was stuff I could do with a $2 pad of lined-paper. Once I felt they had learned their entire alphabet well, we started with "A Reason for Handwriting Book A." Starting with this book, the daily assignments are broken up into four separate days for each lesson, which is great for homeschoolers who do four days of school a week like we do. (We leave Fridays open for writing letters and doing field trips.) On the fourth day of each week's/lesson's assignment, the child writes the verse from which they have been practicing words each previous day.Here's the link to it on christianbook.com where you can see sample pages:
http://www.christianbook.com/Christian/Books/product?item_no=785381&event=CF#curr
That pretty much covers the basics. As far as anything else goes such as science and social studies, that can all be natural learning for those early years. Explore the world around you in a natural and interest-led way and use the library! Please leave your comments if you have any questions or would like any more information. Homeschool blessings!
(I would also like to note that I get nothing by recommending these products. I have simply found them to be such good products that I would like other homeschoolers to experience the same benefits from them as I have!)